Literature / Percy Jackson and the Olympians

"If you're a normal kid, reading this because you think it's fiction, great. Read on. I envy you for being able to believe that none of this ever happened. But if you recognize yourself in these pages — if you feel something stirring inside — stop reading immediately. You might be one of us. And once you know that, it's only a matter of time before they sense it too, and they'll come for you."

Percy Jackson and the Olympians is a middle-grade Urban Fantasy series by Rick Riordan based on Greek mythology. It spawned The Camp Half-Blood Series and eventually the Riordanverse; the Sequel Series, The Heroes of Olympus and The Trials of Apollo have their own pages.

In the books the Greek gods have moved to the United States, and their home, Olympus, is now located at the 600th floor of the Empire State Building. They have many demigod children with mortal humans. Unfortunately, these demigods attract mythological monsters, so they must travel to a safe haven in Long Island, New York, called "Camp Half-Blood", and learn to fight.

The first five books center around the Great Prophecy, which prophesizes that a demigod child of the Big Three (Zeus, Poseidon, and Hades), on their Dangerous 16th Birthday, is destined to make a decision that will save or destroy Olympus. The books get progressively Darker and Edgier as a war with the Titans approaches. These books are:

• The Lightning Thief (2005)
• The Sea of Monsters (2006)
• The Titan's Curse (2007)
• The Battle of the Labyrinth (2008)
• The Last Olympian (2009)

The second set is an interquel trilogy set between the events of The Heroes of Olympus and The Trials of Apollo. The trilogy follows Percy in his senior year of high school as he embarks on quests for the gods to get recommendation letters for college at New Rome University. The books so far are:

• The Chalice of the Gods (2023)
• Wrath of the Triple Goddess (2024)

There are also five companion books:

• The Demigod Files: Includes three short stories and information about Camp Half-Blood.
• The Ultimate Guide
• Demigods and Monsters
• The Demigod Diaries: Includes three additional short stories as well as a short story by Rick Riordan's son, Haley.
• Percy Jackson's Greek Gods: Percy retells the stories of the Olympians (also touching on a couple extras, like Hades and Persephone) in his own words — that is to say, sarcastically, with lots of pointed commentary, bias, and criticism.
• Percy Jackson's Greek Heroes: Released in August 2015, it's the same premise as the previous one, only with the various heroes instead of gods.

The series has also had a few adaptations:

• Graphic novel adaptations of all five books.
• Percy Jackson and the Olympians: Two films based on the first two books of the series, Percy Jackson & the Olympians: The Lightning Thief, and Percy Jackson: Sea of Monsters.
• The Lightning Thief: A musical of The Lightning Thief, the first book in the series.
• Percy Jackson and the Olympians (2023): A live-action series on Disney+, announced on May 14, 2020. Unlike the film adaptations, Riordan is more actively involved with the development of the series. The first two episodes will release on December 20, 2023.

Now has a Best Installment Crowner.

Tropes for the crossover stories The Son of Sobek, The Staff of Serapis and The Crown of Ptolemy are on the Demigods & Magicians page.

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This series provides examples of:

A

• Abduction Is Love: In Percy's retelling of the stories of the gods, he has Hades actually going to Zeus for advice on how to court Persephone. Hades has the idea to talk to Demeter and ask for permission or to declare his feelings to Persephone, but Zeus goes for one of his favored methods, "I suggest kidnapping." And the rest is history.
• Abusive Parents: Many gods neglect their children. It's the biggest reason why there is a Titan army. There are kids who are never claimed. They get stuck at the Hermes cabin.
  • Nemesis, God of Balance and Revenge, to Ethan. The one time they meet, she blinds his left eye with the promise that he would bring balance to the world once again.
  • Kronos the Titan, father of the gods, who ate his own children to keep them from rebelling against him.
  • In the first book, Percy's stepfather, "Smelly" Gabe, treats both Percy and his mom like dirt. At the end, Sally Jackson uses Medusa's head to turn Gabe into a stone statue.
• Achilles' Heel: Figuratively and literally. Taking a dip into the River Styx enables you to become invincible so no weapon will harm you, except at a tiny spot somewhere on your body. Along with Achilles' actual heel, the final book has two — a spot on Percy's back and a spot near Luke's armpit. Additionally, the tiny weak spot isn't the only Achilles' Heel of taking a bath in the Styx. While you Take a Level in Badass, in addition to becoming invincible, you do so basically by turning your body up to eleven, meaning you need especially long periods of rest between fights. Meaning that if someone throws enough Mooks at you, you will drop from exhaustion faster than a normal person.
  • In addition, it is implied that bathing in the Styx amplifies the bather's own personal "fatal flaw" — you become heavy with one emotion (such as pride) that can be used against you. This is somewhat subverted in that the weakness that Percy has, personal loyalty, causes problems but doesn't actually link to a defeat in the finale.
• Achilles in His Tent: Two examples from The Last Olympian:
  • Clarisse, in a deliberate echo to the myth, initially refuses to participate in the final battle over an inter-cabin squabble. She only joins the battle when her best friend charges out disguised as her and gets killed.
• Action Girl: The female demigods are just as capable in a fight as their male counterparts. The same applies to the Hunters of Artemis, an Amazon Brigade.
• Adaptation Species Change: Procrustes was a human (or demigod in some tellings) murderer in the original mythology. Here, he's a monster.
• Aerith and Bob: The cannibals in The Sea of Monsters are: Marrow Sucker, Skull Eater, and... Joe Bob.
• Affably Evil: Geryon. He makes omelettes from the eggs of endangered species, slaughters the sun cattle, sells to Kronos' army, and enslaves Nico. On the other hand, he doesn't interfere with quests, holds barbecues for his captives, and gives people a grand tour of his ranch.
  Annabeth: You're a monster.
  Geryon: What gave it away? Was it the three bodies?
• All Myths Are True: If it showed up in any Greek mythological story, it's not a myth. And it probably wants to kill you. When Percy asks about whether or not God exists in the first book, he's told by Chiron that he would be getting "metaphysical". Apparently the Olympians don't know if He exists any more than we do.
  • The Kane Chronicles, which is set in the same universe, actually takes this a step further by stating all Egyptian gods are real. Moses of the Abrahamic religions is also mentioned.
    • There was also a line in The Kane Chronicles about the Faust family being deeply involved with supernatural whatsits as well, so it can be assumed that European fairy tales might be fair game as well.
  • In the The Trials of Apollo series, Apollo mentions that that the Aztec god of the sun can help keep the sun spinning in his absence.
    • Nigerian mythology makes a brief cameo as well: it's implied that Olujimbe, or "Jimmy", is a Yoruba demigod (likely the son of Shango).
    • Apollo also mentions nearly crashing his sun chariot into a Chinese celestial dragon.
• All There in the Manual: The Demigod Files and Demigods and Monsters. (The former is significant in that it explains a lot of the "dragon" business in The Heroes of Olympus and gives Clarisse Character Development.)
• Always Save the Girl: Aphrodite urges this course of action on Percy in The Titan's Curse.
• Amazon Brigade: The Hunters of Artemis, an all-female team that hunts supernatural monsters alongside their patron.
• Annoying Younger Sibling:
  • Nico to Bianca, and Tyson to Percy at first.
  • Apollo to Artemis; no matter what he says, in most traditions she was born first (and Percy Jackson's Greek Gods confirms it to be the case here too).
• Apocalypse Maiden: Thalia in The Titan's Curse. In a similar vein, Percy himself.
• Army of The Ages: The fortress of the Greek god Hades is guarded by dead soldiers from all of history: Skeletal Roman legionnaires with spears are joined by undead US Marines with assault rifles.
• Arson, Murder, and Jaywalking:
  • Dionysus playing Pac-Man.
    Dionysus: The world will fall, the gods will die, and I will never achieve a perfect score on this stupid machine!
  • The punishments in the Underworld.
    Even from far away, I could see people being chased by hellhounds, burned at the stake, forced to run naked through cactus patches or listen to opera music.
• Artistic License – Geography:
  • Rick Riordan seems to think that Mount Diablo in California is like some kind of lowland Yosemite mixed with the Australian outback, when truthfully it's just a gentle rolling brown hill with hardly any foliage on it. Anyone who has actually looked at Mount Diablo (even on Google Maps) could tell you the top is NOT a depression with eucalyptus trees, but rather a visitors' center, and there really aren't any cliffs like described. And while it is a plot point, there are not enough — or any — eucalyptus trees surrounding the mountain, certainly not enough to be overpowering. An early morning in the middle of winter might not be freezing, but it's cold. And the Golden Brown Berkeley hills are just that, golden brown — during summer. They do, in fact, get green(ish) in the winter.
  • The Lightning Thief has a scene where Percy jumps from the top of the Gateway Arch straight into the Mississippi River, likely due to a common misconception that the Arch spans the river (it does not). Considering that the Arch is a hundred yards or more from the river under ordinary circumstances, with some wide concrete walkways, a huge 64-step grand staircase, and a road in between, he'd need a hang glider to achieve this. (See this photo◊ for reference.) Even during flood season, the closest the river has ever been to the Arch is halfway up the staircase. However, this is explained away with Percy's water powers.^note The book itself says he jumped, with no mention of his water powers activating.The Graphics Novel fixes this, by having Grover try to catch Percy with the Hermes shoes only to drop him into the water.
• Ascended Extra:
  • Hestia, who appears in the first book stoking the campfire at Camp Half-Blood, but Percy doesn't find this out until The Last Olympian.
  • Rachel Elizabeth Dare, who appeared briefly in The Titan's Curse at Hoover Dam. In the next book, she attends the same school as Percy, and by the end of The Last Olympian, she has become the new Oracle (which carries over into The Heroes of Olympus).
• Assuming the Audience's Age: The intro to The Lightning Thief says if you think you are a half blood, you should stop reading, but if you're a normal kid who thinks the story is fiction, you should keep thinking that.
  If you're a normal kid, reading this because you think it's fiction, great. Read on. I envy you for being able to believe that none of this ever happened. But if you recognize yourself in these pages — if you feel something stirring inside — stop reading immediately. You might be one of us. And once you know that, it's only a matter of time before they sense it too, and they'll come for you.
• Attack Its Weak Point: Luke and Percy, due to their dips in the River Styx. It's also implied that Ethan Nakamura, the son of Nemesis, can identify weak points as part of his powers. When confronted by him, Percy is instinctively aware that Ethan knows exactly where his Achilles point is.
• Attack of the 50-Foot Whatever: Happens a few times. Some examples are Polyphemus, the Talos robot and the Drakon.
• Attention Deficit... Ooh, Shiny!: All demigods have ADHD, which is a sign of their battlefield reflexes and greater sensory perception. The disorder is handled well, though, since Riordan's son has ADHD and he knows what he's talking about.
• Attending Your Own Funeral: Percy is launched out of a forge in Mount Saint Helens in The Battle of the Labyrinth and wakes up on Calypso's island. He spends the equivalent of two weeks there. Hephaestus then enchants a raft, allowing Percy to drift back to Camp Half-Blood. When he arrives, he walks in on his own funeral just as the campers prepare to torch his shroud.
• Author Avatar: Percy is basically the representation of Riordan's son, who has ADHD and dyslexia.
• Author Tract: Riordan apparently isn't a fan of Pepsi, since most characters drink Coke and the one character who does get a Pepsi (Hephaestus) has it accidentally spilled on him before he even has a chance to drink it.
• Awesome, but Impractical: After taking a dip in the River Styx, Percy takes a major level in badass, but has to rest after almost every fight he gets into.

B

• Backstory Invader: The Mist can be manipulated to create Fake Memories of a person. For example, after Mrs. Dodds (Percy's teacher and a servant of Hades) attacks Percy and is killed, a new teacher named Mrs. Kerr mysteriously appears to take her place, and nobody but Percy remembers that Mrs. Kerr hadn't always been their teacher.
• Badass Army: The demigods as well as Kronos's army of monsters.
• Badass Bookworm: Annabeth most prominently, but her dad and Daedalus count too.
• Badass Normal:
  • Comparatively. Children of Athena don't really have any supernatural powers, but their sheer intelligence and strategy makes them be very competent and powerful fighters and hold equal ground to any other demigod.
  • Annabeth's dad Frederick, Percy's mom Sally, and Paul Blofis play this straight, being mortals who are more than willing to charge into battle to defend their children.
• Barrier Maiden: Thalia in tree form protects Camp Half-Blood from monster invasions.
• Bastard Bastard: Mostly demigods who fall on the 'resentment' side of the scale, but some of the gods' children are just bad people, especially the monstrous ones.
• Bathroom Brawl:
  • The Lightning Thief has Clarisse La Rue and some of her sisters from the Ares cabin try to push Percy's head into the toilet, which devolves into a short brawl. It ended by Percy soaking them in toilet water.
  • In Battle of the Labyrinth, the Empousai attack Percy and co. in the bathroom.
• Beethoven Was an Alien Spy: It seems that most any legendary figure in the history of Western civilization who did something important was a demigod: George Washington was the brainchild of Athena, Thomas Jefferson was one of Zeus — given how he is a judge of the Underworld since all of the judges are (and it must have had something that helped the colonists win the American Revolutionary War), and Harriet Tubman was a daughter of Hermes.
  • Oh, and by the way, Edward Teach (also known as Blackbeard) is a son of Ares. He and his crew have been trapped in Circe's cage as guinea pigs for about 300 years, so when they are turned back into humans by Percy's vitamin pill, they take no hesitation in ransacking the isle as revenge.
• Belligerent Sexual Tension: Between Percy and Annabeth throughout the entire series.
• The Bermuda Triangle: With the mythological sites that used to be around Greece and Rome now located in North America, this location got to take the title of the Sea of Monsters from the Mediterranean Sea.
• Berserk Button: Echidna really hates Australia for naming "that ridiculous animal" after her.
• Best Her to Bed Her: This seems to be how romance works at Camp Half-Blood: "If a girl keeps trying to kill you, it means she's into you."
• Betty and Veronica: Subverted with Annabeth and Rachel; both are very nice girls who like Percy (the Archie). If one had to get technical, either one could be considered the Betty or the Veronica; Annabeth could be the Veronica since she's meaner and more violent (but not terribly) than Rachel, who is almost always polite and well-mannered (since she's upper-class) and because of that could be considered the Betty. Or one could consider Annabeth to be the Betty, since she's known Percy for longer, is best friends with him, and is blonde, while Rachel, in true Veronica fashion, becomes friends with Percy later on and interferes in Percy and Annabeth's budding romantic relationship (albeit unintentionally). Both girls are considered to be very good-looking by others, furthering the justification.
• Big Applesauce: It's where Mount Olympus is located and Percy's home town.
• Big Bad: Kronos, the Titan King. He serves as Sealed Evil in a Can manipulating Luke until the fourth book, where he comes to earth by possessing Luke Castellan.
  • Though as he is Sealed Evil in a Can for the first four books, each of those books also has its own Big Bad.
    • The Lightning Thief: Luke.
    • The Sea of Monsters: Polyphemus and Luke.
    • The Titan's Curse: General Atlas.
    • The Battle of the Labyrinth: King Minos and Kronos himself, who is finally free via half-blood host Luke.
• Big Brother Bully: Triton is quite cold to Percy when they meet in The Last Olympian, acting like Percy is lazy, emphasizing that he (Triton) is Posideon's heir, and telling Poseidon that he, Triton, will not fail in his duties.
• Big Damn Heroes:
  • Quite often in the books, especially in The Last Olympian. Special mention should probably go to Hades, the Ares Cabin, and the Party Ponies, who get three moments in the series.
  • This is Mrs. O'Leary's sole reason for existing. Well, this and Comic Relief.
• Big "NO!": Several.
  • Kronos. Not so much dragged out, but it was in all caps, and the idea remains the same.
  • Tantalus' "Nooooooooo!" in The Sea of Monsters after Dionysus sends him back to the Underworld.
  • Sisyphus in The Demigod Files. "NOOOOOOO!"
  • Zoe, when Atlas is about to stab Artemis.
  • Atlas being returned to his chains. "NOT AGAIN!"
• Bilingual Bonus: When pretending to be Polyphemus' bride, Grover claims to be wearing "Eau de Chèvre" perfume to explain why he smells like goats. Chèvre is French for "goat".
• Birthday Beginning: Inverted. The fourth book ends on Percy's birthday. The entire series leads up to his Dangerous 16th Birthday, but the epilogue ends things somewhat later.
• A Birthday, Not a Break: Percy forgets his sixteenth birthday.
• Black-and-Gray Morality: Help the Gods who are often jerkasses and sometimes cause problems, or serve a Titan who devoured his own kids and uses humanity as a source of cheap amusement or as a snack.
• Blessed with Suck: One of the common themes in Greek mythology is that Blessings and Curses are essentially the same. Having a perfect understanding of ancient Greek, and whether you are willing to tolerate having ADHD as a side effect of your supernatural combat instincts. And then there's all the monsters you attract, especially if you carry a cell phone. Also the more powerful you are as a demigod, the more monsters you attract. (Not to mention the added bonus of probably ending up having a prophecy about you).
  • Grover has managed to locate half-bloods on three separate occasions. Unfortunately, all of them have been children of the Big Three, and thus the most likely to die.
• Blond, Brunette, Redhead: The three major female characters in the book: Annabeth, Thalia, and Rachel.
• Born of Magic: Annabeth Chase is this, which explains why she exists despite the fact that her mom made a Vow of Celibacy. In The Battle of the Labyrinth, she tells Percy that her mother created her as a "gift" to her father.
• Bound and Gagged: Several times in the series, for the enjoyment of the fans.
• Bowdlerise: Anyone should know that Greek mythology is not exactly kid-friendly, so the author had to intervene. For example, it's stated Kronos cut Uranos "to bits". This is somewhat imprecise — technically, it was only two bits, the bits Uranos loved most, and the rest of Uranos.
• Bring Them Around: In The Last Olympian, Nico goes to great lengths to persuade Hades to come and help the Olympians fight; whatever they had done to each other, they were family.
• Brick Joke: There were a few throwaway lines about lost pizza deliverymen in this series. In the second sequel series, Apollo reveals this was his fault.
• Broken Bridge: Inverted. In the fifth book, Percy destroys the Williamsburg Bridge in an attempt to stop Kronos's army.
• Butt-Monkey: Humanity in-universe, or at the very least Westerners. Whether it's tourists being turned to stone by Medusa, children being lured into a Lotus-Eater Machine for eternity, or innocent shoppers being stretched to death or hacked up by Procrustes, it sucketh verily to be a human in the Percy Jackson universe.
  • And if humans are lucky enough to avoid those fates, then they usually end up being the innocent victims of divine temper-tantrums, cosmic playthings for the gods, and in general are oblivious to the world around them.

C

• Calling Me a Logarithm: Used in The Titan's Curse. In this case, it is an insult, but it doesn't change the fact that Thalia's not sure what it means.
  Zoe Nightshade: You challenge my skills, you scullion? You know nothing of being a Hunter!
  Thalia Grace: Oh, scullion? You're calling me a scullion? What the heck is a scullion?
• Calling the Old Man Out: In a series saturated with Parental Abandonment, you know this is coming. It's Luke's whole reason for wanting to tear down Olympus in the first place.
  Hades: (to Kronos) And if there's one thing we can agree on, it's that you were a TERRIBLE father.
• Calling Parents by Their Name: Unless they are speaking directly to them, demigods almost always address their godly parent by their actual name. Even then, they call them "Mother" or "Father" as more of a respectful title than a name.
• The Call Knows Where You Live: Pretty much on a race-to-straight-up species wide scale. The moment a Half-blood accidentally or purposefully does something that uproots the truth of their real heritage, the monsters in the immediate area will smell their divine scent and will mobilize to them like a predator to prey.
• Campfire Character Exploration:
  • In The Lightning Thief, a campfire at their cabin in Montauk is where Percy and his mother discuss Poseidon.
  • A variant in The Battle of the Labyrinth: Percy is watching Nico around the campfire in a dream, and he sees that Nico has started communicating with King Minos' ghost in an effort to save his sister. Also, it's here that Nico abandons his old obsession with the Mythomagic card game.
• Camp Unsafe Isn't Safe Anymore: In The Sea of Monsters, Camp Half Blood is "no longer safe" because someone has poisoned Thalia's pine tree, which usually keeps the camp safe from outside monsters. However, the camp was never safe from anyone on the inside who wanted to hurt anyone else on the inside, as demonstrated by the ending of The Lightning Thief.
• Cannot Spit It Out: A staple of the series; if anyone has any sort of vital information, they will hold it back for longer than necessary. Most often they have their reasons for it, but it still gets very noticeable after a few books. And when they do try to tell straight away, they're generally interrupted by someone or something else before they can get to the point. Of course, this is based on Greek mythology so it's not surprising.
• Celestial Bureaucracy: The Underworld, all the way. You know the Ancient Greek tradition of putting a coin in the dead's mouth to help them pay their passage across the River Styx? Charon charges people's credit cards. And if you're a kid and don't have one? Well, you're kind of screwed.
• Central Theme: Majority of the conflict in Sea of Monsters revolves around Cyclopes. First, Grover is being held hostage by the most infamous Cyclops, Polyphemus. A new prominent character, Tyson, is revealed to be not only be a Cyclops, but a son of Poseidon, and subsequently Percy's brother. Percy learns (or, more accurately, processes) that the majority of Cyclopes are his half-siblings, and struggles accepting this. Lastly, it's revealed Annabeth has trauma related to Cyclopes, because she, Luke, and Thalia ran into one on their way to Camp Half-Blood, and she believes that, if that hadn't happened, they would have had enough time to make it to camp with Thalia alive.
• Cerebus Syndrome: Starting with The Titan's Curse, the series gets steadily darker with the deaths of major good-guy characters and more mature themes.
• Changeling Fantasy:
  • Percy and about ninety percent of his friends. Demigods are generally unaware of their divine parent's identity until they go to Camp Half-Blood, and even then they don't usually find out from their parent personally.
  • Finding out the other parent is often a bad thing. For starters, some parents were kind of absent. One can understand not telling a kid since they'd brag^note Hey, it didn't turn out so well for poor Phaethon!, but when they need to know and they aren't there… well…
    • Things are improving in The Heroes of Olympus, however, as demigods were claimed instantly and the godly parents actually talk to their children.
• Chekhov's Classroom: Chiron points this out about Percy's Greek History before Percy knows anything. Then it is taken to the extreme when he goes to Camp Half-Blood.
• Chekhov's Gun: In the first book, Percy uses Annabeth's fear of spiders to snap her out of the lotus trance.
• Chekhov's Gunman: Remember Circe's assistant in The Sea of Monsters? Now read the second book of the second series. Also, that little girl at the campfire in the very first book turned out to be rather important...
• Chocolate of Romance: It's explained that Aphrodite, goddess of love, was attracted to Silena's father because he owned a chocolate factory.
• Circles of Hell: What did you expect? This is Greek mythology. Within the Underworld, there's the Isles of the Blest at the top, Elysium below that (or encircling them), the most widely populated Fields of Asphodel, and then the Fields of Punishment. Then there's also the fact that you get special punishment from Hades himself if you're sufficiently bad. It's implied that your soul gets sewn into his clothes a little bit later.
• Classical Chimera: While on the Gateway Arch, Percy faces a Chimera (initially disguised as a chihuahua) alongside its mother Echidna before being forced to retreat. While at first depicted as having a lion's head, a goat's body, and a snake for a tail, Percy Jackson's Greek Heroes describes it as having the hindquarters of a dragon and a goat's head on its back. Percy explains this as monsters often changing their appearances.
• Classical Cyclops: Cyclopes appear as giants with a single eye in the middle of their foreheads. They're incredibly strong and tend to be gifted smiths, but are also considered to be extremely ugly. Three distinct groups of them exist:
  • The Olympian cyclopes are the many, many children of Poseidon and assorted nymphs and nature spirits. This makes them all Percy's half-brothers, a subject he tends to find uncomfortable. They chiefly serve their father as smiths and soldiers, and many of them live in his realm beneath the sea — they can breathe water thanks to their parentage. They're chiefly on the side of the heroes, but this isn't universal — Polyphemus, most notably, is one of their number.
  • Hyperborean cyclopes are largely independent, and tend to live in small groups on their own, but retain their skill with metal and machinery. They're more intelligent, but no less hostile than their southern kin, and sided with the Titans during the second Titanomachy.
  • The Elder Cyclopes, Arges, Brontes and Steropes, were the original cyclopes born to Ouranos and Gaea and locked in Tartarus by their father. They're the weaponsmiths of the gods, aiding Hephaestus in his forges and having created most of the gods' weapons, but aren't particularly active otherwise.
• Coins for the Dead: Charon expects the dead that he ferries over to have a method of paying him:
  I don't suppose you have coins for passage. Normally, with adults, you see, I could charge your American Express, or add the ferry price to your last cable bill. But with children ... alas, you never die prepared. Suppose you'll have to take a seat for a few centuries.
• Connected All Along: Percy mentions that the weather had been weird since Christmas, with it later being revealed the reason for this is because that's when Zeus's lighting bolt was stolen. It's also mentioned Camp Half-Blood had a field trip to Mount Olympus during the Winter Solstice (AKA December 21st, four days before Christmas). As it turns out, this is when the bolt was stolen, by Luke.
• Cool and Unusual Punishment: Percy mentions being forced to listen to opera music for eternity as one of the tortures inflicted in the Fields of Punishment.
• Corrupt Corporate Executive: One of the spirits that Percy, Annabeth and Grover see getting stopped by a security guard at the Underworld security checkpoint in The Lightning Thief is one that Percy recognizes as a televangelist who had promised to raise millions of dollars for orphanages... but was then caught embezzling it and pocketing it for himself to spend on his own mansion. He was then killed in a police chase after his Lamborghini ran off a cliff.
• Creator Provincialism: The United States is literally the current center of western civilization, even though it's noted that this is not necessarily a good thing. Canada is mentioned, but only because it's where Laistrygonian giants are from.
  • In the second series, Canada is featured much more extensively, with one of the main characters being Chinese-Canadian, his mother serving (and dying) with the Canadian military presence in Afghanistan, and much of the first book taking place there.
• Crossover Cosmology:
  • The Roman god Janus appears in the The Battle of the Labyrinth (he doesn't have a Greek equivalent). invokedWord of God said in an interview that the Roman gods exist but they are younger than the Greek gods. This is expanded on in the second series where the Greek and Roman gods (the ones that exist in both mythologies, anyway) have split personalities, and a main plot point is to get their two aspects to reconcile.
  • The Kane Chronicles, which features Egyptian gods, also takes place in the same universe. Percy and Annabeth team up with Carter and Sadie Kane in a trilogy of short stories: The Son of Sobek, The Staff of Serapis and The Crown of Ptolemy. They mutually agree that mixing Greek and Egyptian magic is dangerous and vow to restrict contact between their respective worlds.
  • The series Magnus Chase and the Gods of Asgard, based on Norse mythology, is also set in the same universe, with the protagonist Magnus being Annabeth's cousin.
  • The Trials of Apollo mentioned Aztec, Babylonian and Chinese mythologies, with Apollo pretty much stating that every belief system is true, including science (according to him, the sun goes across the sky because people believe science makes it go across the sky).
• Cruel and Unusual Death: Bianca is electrocuted inside a giant bronze automaton in New Mexico. Zoe is killed by a combination of dragon poison and her father on Mount Tamalpais. But the laurels definitely go to Silena, who's facially disfigured by the acid breath of a giant, two-hundred-foot-long worm and gets launched into the pavement.
  • Silena's death doubles as invokedFridge Horror when you think about whose child she is. A daughter of Aphrodite essentially having her face melted with acid? That would be like Annabeth losing all of her intelligence and dying because of it. Or Percy dying of drowning!
• Crystal Dragon Jesus: Consciously averted. Percy initially equates the concepts of God to the Greek gods, but Chiron is quick to point out that the capital-G God is "metaphysical" and therefore in a different category from the Olympians. However, the topic is teased constantly with... interesting implications. The Kane Chronicles features a flashback to Moses dueling House Magicians, and it's mentioned in The Sword of Summer that Thor's still peeved over Jesus never accepting a fight challenge.

D

• Dangerous 16th Birthday: Percy's prophecy. When he turns 16, he will make a decision that will save or destroy Olympus.
• Dangled by a Giant: When Percy and Annabeth arrive on Polyphemus' island, Annabeth attempts to distract the giant Cyclops by putting on her invisible cap and taunting him while pretending to be his old enemy, "Nobody." Unfortunately, Polyphemus finds her by the sound of her voice, grabs her, dangles her upside down and shakes her so that the cap falls off her head.
• Darker and Edgier: The series gets progressively darker with each following book, capping off with the deaths of Silena, Beckendorf, Luke and more and quite a few tearjerkers in The Last Olympian.
• Dark Secret: Zoe is the daughter of Titan general Atlas, Kronos' right hand. She was also the mastermind behind at least one of Hercules' great victories; it's implied she may have helped him with others. Nico di Angelo being the son of Hades is treated as one (of the fewer people know the better catergory).
• Deadpan Snarker: Pretty much everyone is a deadpan snarker, though Percy probably gets the most in. The chapter titles are almost always deadpan snark in some way: "I Accidentally Vaporize My Pre-Algebra Teacher" is the first.
• Dead Person Conversation: With King Minos, Bianca, Achilles. Nico di Angelo does this regularly, being the son of Hades.
• Death Is Cheap: The monsters and Luke/Kronos.
• Decided by One Vote: After Grover reveals to the Council of Cloven Elders that Pan is dead and disappeared in The Battle of the Labyrinth, he is initially disbelieved. However, Dionysus does and argues on his behalf. The voting body is divided, and come time to vote, Dionysus' vote counts double (being a god), and forces a tie. The group thenceforth splits in two, based on whether they trust the new information.
• Defanged Horrors: Some monsters aren't as scary as they seem. For example, Cerberus is a Rottweiler who likes to play with red balls.
• Despair Event Horizon: Percy has one in The Last Olympian when Silena dies after revealing she was The Mole, Rachel cuts him off, Annabeth is angry at him over Luke and Rachel, his parents are caught in cursed sleep, Olympus seems about to fall, and he'd seen the cruel acts of Zeus, Hades, and Hermes. He almost lets Hope out of Pandora's Box and surrenders, but after remembering some inspiring words from Chris Rodriguez and Nico, he instead gives the jar to Hestia and fights on stronger than ever.
• Devour the Dragon: Kronos possesses Luke's body in The Battle of the Labryinth.
• Did You Just Flip Off Cthulhu?:
  • Rachel threw a blue plastic hairbrush at Kronos.
  • This gem from Percy himself:
    Percy: But I've never even been to Olympus! Zeus is crazy!
  • This gem from Maria di Angelo:
    Maria di Angelo: Zeus is un imbecile.
• Did You Just Punch Out Cthulhu?:
  • It took all the Olympians, Poseidon's army, a cross country trip through the USA and the entirety of the final book but they did defeat Typhon the Storm Giant.
  • At the end of the first book, 12-year-old Percy, with barely any training, manages to beat Ares, the several-thousand-year-old god of war.
  • In The Last Olympian, after Percy bathes in the river Styx and gets the Achilles curse in the Underworld, he faces off against Hades' army and wins.
• Direct Line to the Author: Riordan himself is a Senior Scribe at Camp Half-Blood, publishing the books as works of fiction. Even so, Percy takes time in the first book to warn the readers that if they think they're a half-blood, to shut out that feeling and remember that it's just fiction. This continues in The Heroes of Olympus.
• Disability Superpower: All half-bloods have ADHD, which enhances their battle awareness, and dyslexia, which is caused by their brains being hardwired for ancient Greek. The ADHD thing actually has basis in real life; it's believed that the condition originates from survival instincts from humanity's hunter-gatherer days.
• Distracted by the Sexy: Percy is reduced to speaking gibberish when speaking to Aphrodite in The Titan's Curse. His narration also notes that she's too beautiful to describe.
• Divine Parentage: Percy's father is Poseidon, the Greek god of the sea. Many of his friends are also children of various other gods.
• Does This Remind You of Anything?: Percy says he is expecting the Underworld entrance to be a set of pearly gates or a black portcullis. The actual result is... an airport security checkpoint. There's an EZ Death line, as well as two Attendant on Duty lines that crawl at a very slow rate. Also, the spirits in the waiting room have been there for a few hundred years.
• Doomy Dooms of Doom: Chapter 14 in The Sea of Monsters is titled "We Meet the Sheep of Doom". These are sheep who rush and kill a poor defenseless deer right in front of Percy and Annabeth on Polyphemus's island. Said deer goes from being a living creature to being a pile of bones picked entirely clean in under two seconds.
• Downer Ending: Percy Jackson and the Greek Heroes concludes with the story of Jason dying alone, his quest failed, his children dead by his wife's hands, and despised by everyone.
  Percy: And if that isn't a great ending for this book, I don't know what is!
• Down in the Dumps: In The Titan's Curse, Percy and crew wander into the "junkyard of the gods" in Yuma Claw, Arizona and end up setting off a giant automaton. Naturally.
• Dramatic Thunder: It tends to happen a lot thanks to Zeus, so naturally it's lampshaded by Percy.
  Percy: Is there anything we can say without it thundering?
• Dream Spying: Percy eavesdrops on villains' conversations pretty much every time he dreams (which is a lot), although the aversion of As You Know means the information he gathers is rather cryptic. Played with in The Titan's Curse, when one villain reveals that she let Percy listen in on the conversation specifically to kill his morale.
• Drives Like Crazy:
  • The Gray Sisters. Given they're all fighting over that one eye while behind the wheel, it's amazing they can avoid getting into any accidents.
  • Thalia driving the airborne sun chariot in its schoolbus form. Mainly due to her acrophobia. She torches a New England village while flying it, and doesn't land smoothly enough at Camp-Half Blood, prompting Apollo to say they should look and hope they haven't burned up anyone important. She can drive well on land, though.
• Dodgeball Is Hell: A bit more literally than you might think at the beginning of The Sea of Monsters.
• Duel to the Death: Percy regularly fights these. Among them is his battle with his much older half-brother Antaeus in The Battle of the Labyrinth.
• Due to the Dead: Heroes are cremated with funeral shrouds embroidered to indicate their divine parentage and just what made them great.
  "We need a shroud. A shroud for the son of Hermes."
• Dying Moment of Awesome: Anyone who dies goes out with a really, really loud bang. In Charles Beckendorf's case, quite literally.
• Early-Bird Cameo:
  • Hestia. Pay attention to that little girl at Camp Half-Blood in The Lightning Thief.
  • Reyna and her sister Hylla are Circe's servants/assistants in The Sea Of Monsters.
  • Rachel appears briefly but memorably in The Titan's Curse by way of helping Percy hide from Atlas' zombie warriors, then demanding an explanation. Percy is shocked in-universe when she shows up again at his high school in the next book, and recognizes him.
  • Gleeson Hedge has a cameo in The Last Olympian as the satyr who wrote Grover from Toronto.

E

• Early-Installment Weirdness:
  • This is the only series that Riordan has written with Monochrome Casting at play. The main heroes are all implicitly white, and even Nico, an Italian, becomes increasingly pale due to time spent in the Underworld. All other minority characters are rather secondary at best. It wouldn't be until The Heroes of Olympus that Riordan started diversifying his casts.
  • Lightning Thief is the only book in the series that doesn't mention the Great Prophecy.
  • The Mist, while present, seemed to be less powerful in the first book. Grover always hides his goat legs and hooves so no human sees, but later books have Percy do stuff like walk a hellhound in plain sight with no mortal around batting an eye because the Mist disguises it was a poodle. It's also mentioned that, as young child, Percy was able to tell a stranger was a Cyclops apparently without the Mist concealing it, but in the next book, Percy doesn't notice that Tyson (who was his best friend for an entire year) only has one eye because of the Mist.
  • In the first and second book, the demigods make references to all technically being extended family on their godly side. This was before the series established the only godly DNA that counts is your parent, ergo not making any demigods related beyond siblings.
• El Cid Ploy: Silena disguises herself as Clarisse to lead the children of Ares into battle in the final book. She dies just as the real Clarisse shows up.
• Eldritch Abomination: Maybe the gods; definitely Typhon and the Titans.
• Engineered Public Confession: Percy needling Luke into admitting he poisoned Thalia's tree in front of an Iris message directly to the camp head's office.
  Percy: You poisoned the tree, you betrayed Thalia, you set us all up — all to help Kronos destroy the gods.
  Luke: You know that! Why do you keep asking me?
  Percy: Because I want everybody in the audience to hear you.
• Embarrassing Last Name: Gabe Ugliano? Rebellious streak aside, there's absolutely no way Percy's mom would have sacrificed her maiden name for that surname.
• Escaped from Hell: The Underworld is supposed to be the ultimate prison, and it's constantly said that no one, not even the greatest heroes could escape. Percy does it when he's twelve.
• Establishing Character Moment:
  • Percy is introduced trying to defend Grover from a bully even though getting into another fight could get him expelled.
  • Annabeth appears utterly unimpressed with Percy killing a Minotaur and is more interested in pumping him for information and snarking at him.
    She glanced down at the Minotaur horn in my hands, then back at me. I imagined she was going to say "You killed a Minotaur!" or "Wow, you're so awesome!" or something like that. Instead she said: "You drool when you sleep."
  • Grover himself is established pretty well in the above scene — he's glumly taking the bullying from someone he could probably get to shove off if he really wanted, and practically holding Percy in his seat to keep him from getting in trouble.
• Even Evil Has Standards: "The Sword of Hades" story in The Demigod Files revolves around one of Hades' weapons being stolen by minions working for Kronos. When Percy, Thalia, and Nico question why Kronos didn't steal it himself, Persephone reminds them of the Ancient Law that says no immortal being can steal from another one, and says that even Kronos must abide by that Ancient Law.
• Everyone Can See It: Between Percy and Annabeth.
• Everybody Hates Hades: Averted and invoked by many, but also discussed extensively and eventually rectified in the books.
• Everybody Loves Zeus: Averted. Most characters actually hate his guts.
• Everyone Is Related: Technically, with few exceptions.
  • This is sort of subverted in The Last Olympian where it's explained that gods have no DNA so it's totally not creepy for half-bloods from different godly parents to date, like Silena Beauregard to Charles Beckendorf.^note  Aphrodite is the daughter of Ouranos, thus the half sister of Kronos and Rhea. That makes her Hephaestus' grand aunt. But is ignored since the gods do not have DNA and the relation is fairly distant. They do specify that two demigods from the same parent (a son and daughter of Athena, for example) would never ever consider dating.
  • In The Titan's Curse Thalia is very visibly smitten with Apollo, who is her half brother. During his own series Apollo realises that he kinda flirted with his own half sister and is briefly disgusted.
• Everything Makes a Mushroom: In the second book, Tyson and Percy, playing with chemicals, make a "miniature mushroom cloud" near the trash can.
• Everything's Better with Rainbows: The ever-handy Iris message. It requires a spray of water vapor to create a rainbow, so artificial sources are used:
  • In The Lightning Thief, when Percy, Grover and Annabeth are in Denver and contacting Luke at camp, they utilize the spray machine of a self-service car wash.
  • In The Sea of Monsters, the wake kicked up by Percy and Annabeth's lifeboat allows them to create an Iris message intended to go to Chiron, who unfortunately is in the middle of a noisy party, leading to the communication breaking up.
  • Starting in The Titan's Curse, Percy has a special fountain in his cabin with gold drachmas at the bottom that allow him to communicate with others when necessary.
• Evil Is One Big, Happy Family: Monsters may hunt down and terrorize young half-bloods, but when some half-bloods decide to rebel against the gods under the influence of the titan Kronos, monsters joined up with them under the united banner of the Titan Army. Funnily enough the monsters will sometimes talk about how much they like eating half-bloods in the presence of Kronos-aligned half-bloods (like Agrius and Oreius in The Sea of Monsters).
• Exactly What It Says on the Tin: The chapter titles do this a lot, usually by removing any context and most mythical elements, making them sound bizarre and hilarious, at the expense of making Percy sound like a madman. The first chapter of the first book is called "I Accidentally Vaporize My Pre-Algebra Teacher".
• Exhaustion-Induced Idiocy: Early on, the heroes stumble into a novelty statue shop that the reader will immediately peg as Medusa's lair. Percy explains that yes, it was dumb, but they were exhausted and had been staggering through the woods of New Jersey for a long time.
• Eyepatch of Power: Ethan Nakamura has one that was given to him by his mother with the promise that he will help to restore balance to the world. He does, but not in the way he thought he would.

F

• Fallen Hero: Most of the demigods who turned their backs on the gods and joined Kronos' army, but most prominently Luke. He even has the Louis Cypher allusion in his name to solidify the fallen angel vibes.
• Fantastic Livestock: Geryon's Triple G Ranch has many types of monsters from Greek mythology, including hippaelektryons, flesh-eating horses, and giant scorpions.
• Fatal Family Photo: Beckendorf apparently took out a picture of his family shortly before going to blow up the Princess Andromeda.
• Fatal Flaw: Played straight with Annabeth, Percy, and the entire Hades bloodline. Played with in that Athena points out Percy's fatal flaw, but it never ended up being his undoing — the most we see was Percy getting reminded during The Last Olympian to stop trying to fight every single battle and save everyone himself, since he'd wear himself into the ground that way.
  • invokedInterviews confirm Luke's fatal flaw is wrath. He's blinded by anger at the gods and lashes out against them, and that same anger and recklessness keeps him from realizing how badly he's screwed up until it's too late to stop the ball rolling. In true Greek tragedy fashion, it ends up killing him.
• Fate Worse than Death: In the fourth book, the last line of the prophecy is "Lose love to worse than death". It would appear that this line refers to Luke when he gets possessed by Kronos.
• Fighting a Shadow: Monsters turn to sand when killed, but eventually return.
  • In The Kane Chronicles reveal that they're being banished to the deeper regions of the underworld, and it takes them awhile to claw their way back out.
  • And in The Heroes of Olympus, this happens even faster due to Gaea's meddling and the chaining of the Doors of Death.
• Fireball Eyeballs:
  • Ares, god of war, has creepy flaming eyes because he's a representation of violence and rage; he normally wears sunglasses to cover them up.
  • Hestia also has flames for eyes, but hers are described as warmer and not as creepy; justified, since she's goddess of the hearth, the literal "home fires."
  • Similarly, Hyperion has miniature suns for eyeballs.
• Fireworks of Love: In The Last Olympian, Percy kisses Annabeth during Camp Halfblood's firework show.
• First Girl Wins: Annabeth is the first named girl introduced who could be a possible love interest for Percy. Despite a brief love triangle between them and Rachel Elizabeth Dare, Percy and Annabeth end up together.
• Final Battle: The battle at Manhattan in The Last Olympian. Kronos, Typhon, and countless monsters, titans, and demigods are attacking Olympus and it's up to Camp Half-Blood and the Gods to defend the place.
• First-Person Smartass: Percy himself. It's probably common among half-bloods as an extension of how they cope with their diagnosed-as-ADHD battle instincts. After all, if you find yourself standing before Hades, god of the dead, who's cloaked in a robe sewn together from souls of the damned, then wondering what some poor saps must've done to get themselves assigned to being his boxer shorts has got to be better than having your mind lock up in fear.]
• Five-Second Foreshadowing: After Nico learns that his sister is dead, he claims that he can feel her being judged in the Field of Asphodel. Percy, confused, asks Nico what he means by "he can feel it." How Nico is able to sense the fate of a deceased soul quickly becomes apparent when it's revealed he's a son of Hades.
• Flirty Step Siblings: A really loose example, but Silena, Aphrodite's daughter, and Beckendorf, Hephaestus' son, are technically step-siblings, seeing as their divine parents are married.
  • While accurate, it should be pointed out that Hephaestus and Aphrodite were an arranged marriage. Most myths state that Zeus had Aphrodite marry Hephaestus so that she would stop causing so many problems with the other male gods and he felt Hephaestus was a person of good character who would be a good husband. While true Hephaestus was also, unfortunately, rather ugly so Aphrodite had numerous infidelities.
  • In other stories, Hephaestus knew what he was getting into and had a good sense of humor about it, hence his prank booby traps of epic proportions.
• Florence Nightingale Effect: Annabeth in The Lightning Thief (even though it takes a while) and Calypso in The Battle of the Labyrinth.
• Fluffy the Terrible: The Mother of all Monsters, the Mighty Echidna, which can put a blowtorch to the St. Louis Arch.
• Foil: Luke for Percy.
• Forced Sleep: In The Last Olympian, Morpheus casts a spell on all of Manhattan. It's spread out so thin that the demigods aren't affected, but all the mortals (except Rachel) are.
• Foreshadowing:
  • In The Lightning Thief, when Percy is still trying to find out his godly father, he mentions attempting various skills, but notes that the only one he really excels at is canoeing. In hindsight that his father is Poseidon, it's not a coincidence that canoeing was the only skill that involved water.
  • While Percy settles into Cabin 11, Luke gives him some toiletries he apparently stole and mentions that his godly father, Hermes, is also the god of thieves... a subtle hint that Luke is the titular Lightning Thief.
  • The backpack Ares gave to Percy returns to him after leaving the Lotus casino, even though he threw it away earlier. This hints towards the backpack's magical quality as a result of it being a disguised helm for Zeus's lighting bolt.
  • In The Last Olympian, after mainly encountering Greek gods and monsters, leading up to the first sequel series, The Heroes of Olympus.
    Percy: (to statue) Are you supposed to be Demeter?
    (statue throws things at him)
    Statue: Everyone thinks I'm Demeter! I'm Pomona, the Roman goddess of plenty!
• A Form You Are Comfortable With: The gods do this, as looking on their true form would burn up mortal beings.
• Freudian Excuse: Some of the half-bloods blame their parents for not loving them, abandoning them, etc. and use this as their excuse for joining Kronos's "dark side".
• Fridge Horror: In-universe. In The Sea of Monsters, Annabeth explains that chain stores like Monster Donut multiply so rapidly because they are tied to a monster's life source. Considering the existence of nationwide chains like Burger King, McDonald's, Wendy's, KFC, Dunkin' Donuts, Starbucks, and the like...

G

• Gas Leak Cover-Up: At the start of The Sea of Monsters, when the Laistrygonians firebomb the gym in their attempt on Percy's life, Percy, Annabeth, and Tyson quickly flee because they're certain they're wanted by the police. At the end of the story, when the quest is over, Chiron tells Percy that he convinced the school officials that the bombing was not his fault by manipulating the Mist to make them think it was just a very badly timed furnace explosion. Percy is still expelled for "ungroovy karma".
• Gaslighting: In order to protect Percy from his true demigod nature, Chiron and Grover spend the first couple of chapters trying to convince him that the Fury who attacked him was a hallucination, with aid from the Mist. Percy is not fooled in the least, due to Grover being a Bad Liar.
• Genre Blindness: Lampshaded once when Percy mentions that they should know they are walking into a trap but after walking for hours, not eating, and craving a bed to sleep on, they tend to do stupid things.
• Giant Enemy Crab: Specifically, Karkinos, a giant monster crab that Percy meets in The Last Titan aboard the Princess Andromeda - it's the same crab that tried to interfere in Hercules' battle with the Hydra. Attack Its Weak Point for massive damage! With some bonus Someday This Will Come in Handy.
• God: Mentioned in The Lightning Thief during a handwave by Chiron.
  Chiron: God, capital-G God, is something else entirely. We won't delve into the metaphysical.
• Godly Sidestep: Soon after Percy learns about the gods, he asks the obvious question and is informed that the gods are "the lower-case 'g' kind" and that they "don't deal in metaphysics." Yes, whether or not God exists is something Olympians don't want to investigate.
  • In The Kane Chronicles, the Egyptian gods state that humans ceased worshipping them because, while they are primordial forces, they are still created beings. That poses some interesting questions in light of Chiron's statement on the matter. Of course, being dangerous jerks who used mortals as pawns tended to destroy respect for them as well.
  • To make things even more bizarre, Magnus Chase and the Gods of Asgard mention that Thor once challenged Jesus to a fight.
• Gods Need Prayer Badly: Played with in that they do not need prayers to exist, since the Titans or more obscure gods like Khione are still alive and powerful after thousands of years. However, they are tied to their realms of influence and Western civilization. The weakening of either in an unspecified way can weaken the god. Being remembered and worship can give the gods a reason to live to prevent them from fading. The most direct case is of Pan. The belief of the satyrs, dryads, and other nature spirits are what have kept him from fading away.
• Go Fetch: Attempted in The Lightning Thief against Cerberus, who ignores it. Then they pull out a ball and play it completely straight. He actually whines and looks disappointed when they leave.
• Good is Not Nice: Let's be honest, the gods are complete assholes. Their pettiness and vanity often end up nearly getting the heroes killed even when they're trying to save the day. Lampshaded by Calypso when she questions Percy on his loyalty to the gods.
  Calypso: Tell me, Percy. I have no wish to argue with you. But do you support the gods because they are good, or because they are your family?
• Greedy Televangelist: In The Lightning Thief, Percy, Grover, and Annabeth encounter a televangelist in the Underworld while he's being taken to the Fields of Punishment. He was caught using donated money intended to help others to buy luxury items like golden toilet seats and an indoor golf course, and died when he drove his "Lamborghini for the Lord" off a cliff during a police chase.
• Green Aesop: Various sea and river creatures get uppity around water pollution, and the quest for Pan eventually turns out to be all about the current state of the environment.

H

• Half-Human Hybrid:
  • The Minotaur is one of the first examples. There are numerous others that number so many we would be tracked down if their names were listed here.
  • The majority of the main cast qualifies as well, though it isn't as physically obvious in their case. It's right there in their name; they're the half-blooded offspring of one mortal parent and one divine parent.
• Hammer Hilt: In The Battle of the Labyrinth, Castor is killed when an attacker strikes him on the head with the hilt of his sword.
• Hawaiian-Shirted Tourist: Poseidon appears like one; it's even mentioned word-for-word in The Lightning Thief.
• Healing Serpent: Ironically Hermes is one, despite the Sadly Mythtaken nature of his Caduceus in real life, due to being the apparent creator of Hermes' Multivitamins, which function much like regular vitamins do in real life. In The Sea of Monsters Hermes' Multivitamins were also able to return Percy and others back to their human forms after being turned into guinea pigs.
• Heaven Above: Whenever Mr. D swears, the sky either clouds up or thunders to let him know the gods are displeased, forcing him to look straight up and apologize to the atmosphere. This is all a formality as it would be ludicrous for the gods to live above Mr. D's camp on Long Island; they live above the Empire State Building instead.
• Heel–Face Revolving Door:
  • Daedalus, a son of Athena who spent thousands of years evading death. While he offered some aid to Luke and his forces, he also aided the demigods of Camp Half-Blood.
  • Prometheus, who originally worked with his fellow Titans before fighting alongside the gods during the first Titanomachy. He then sided with the Titans in the second, claiming afterward that he was only pretending to be on their side.
• Heh Heh, You Said "X": When the gang goes to the Hoover dam, they have a lot of fun saying that they want to use "the Dam Bathroom" and go to "The dam snack bar".
• Hellhound: Several in the series, including the quite nicely oversized hellhound named Mrs. O'Leary.
• Herald: Grover, and most satyrs, who are typically the ones to find demigods and bring them to camp. Chiron as well, showing a special interest in Percy and actually leaving camp to pose as his teacher.
• Heroic Bastard: All of the good half-bloods fall under this, with the possible exception of Athena's children. (It depends on whether or not you can consider children born from thoughts bastards.)
• Heroic Lineage: Percy and the others are descended from gods and are related to many heroes.
• Heroic Sacrifice:
  • Zoe Nightshade, who jumped in front of one of the most powerful Titans in the world to save Artemis.
• The Hero's Journey: Every quest that Percy and co. takes.
• Hero Stole My Bike: In The Last Olympian, Morpheus has put a mass Forced Sleep spell on all of Manhattan except the demigods, who are immune. Percy considers "borrowing" a car to get around, but the streets are so packed he wouldn't be able to get anywhere. He ends up driving around on a scooter, figuring that he'll return it if they survive the battle.
• Hidden in Plain Sight:
  • Labyrinth entrances. There is one inside Alcatraz. You can also find one on the North Shore of Long Island at some ordinary strawberry farm, and one at the Times Square Marriott.
  • If you want to go to Mount Olympus, go to the Empire State Building and get a special card for access to the 600th floor.
  • The entrance to the Underworld is located at DOA Recording Studios.
  • You should never venture near Mount Tamalpais if you are visiting San Francisco. Although in reality there is a weather station up there, there are a lot of very supernatural things going on in the area.
• Historical Domain Superperson: The series is very heavy on Beethoven Was an Alien Spy, practically any historical figure who appears or is mentioned in the series is said to be a demigod. Apparently George Washington was Athena's son, Blackbeard Ares's, and Winston Churchill Poseidon's.
• Historical In-Joke: Just think about it:
  • It's obvious Poseidon's wrath caused Hurricane Katrina.
  • Hades causes an earthquake in Los Angeles, which implies that he probably also caused the San Francisco earthquake of 1906, the Loma Prieta quake of 1989, and the Northridge earthquake of 1994.
  • Edward Teach, Blackbeard, was a son of Ares. And he was not killed in battle with Virginia soldiers. Rather, soldiers captured him and handed him over to Circe, who transformed him and his crew into guinea pigs.
• Honor Before Reason: Percy doesn't want to kill poor, pitiful Polyphemus, given that he's bonding with Tyson as best as he can. So Polyphemus actually lives, and thinks he's sunk Nobody.
• Hold the Line: In The Last Olympian, as Typhon advandces towards New York, the gods have to hold him back before he can destroy Olympus.
• Humans Are the Real Monsters:
  • Grover and the other satyrs believe this, given their belief that humans mistreated the earth.
  • Even Hades, the Lord of the freakin' Dead, thinks this, as the events of the 20th-century led to overcrowding in the Underworld.^note And it's all but stated that Adolf Hitler was his own son.
  • Percy also shows shades of this at first, given that he's dealt with nothing but bullies and his abusive step-father for his whole life. He grows out of this over the course of the first book, however, growing to care for the safety of an innocent family and seeing his step-father as one of the worst examples of humanity rather than being par for the course.
• Humans Are Morons: Given the setting, the vast majority of humans come off as this, incapable of accomplishing anything greater than desk-jockeying without divine parentage.
• Humans Are Special: More like "Mortals Are Special". Occasionally this includes full-blooded humans, though demigods get more focus.
• Hybrids Are a Crapshoot: The plot of the entire series, basically. Being a demigod means you are constantly hunted down by monsters, struggle in a normal society, and are usually painfully killed early in life.
• Hybrid Power: Demigods are often chosen by the gods to do their work because being half-divine and half-mortal, they straddle both worlds and can go places and do things that either mortals or gods cannot.

I

• I Can Still Fight!: Annabeth and Pollux in The Last Olympian.
• Iconic Sequel Character:
  • Thalia Grace does not appear until the very end of The Sea of Monsters and doesn't do anything until The Titan's Curse, but became extremely popular with the fanbase. Her connection with one of the primary characters of The Heroes of Olympus solidified her importance.
  • Ditto Nico di Angelo, who first appears in The Titan's Curse and becomes a major player in The Battle of the Labyrinth and The Last Olympian. And like Thalia, he has a connection to one of the main characters of The Heroes of Olympus.
• I Found You Like This: Percy collapses after fighting the Minotaur outside of Camp Half-Blood. After winning the fight, he awakens inside the camp being tended to by Annabeth Chase.
  • Percy's arrival at Calypso's island in Battle of the Labyrinth. He passes out while being catapulted out of Mount St. Helens, and when he wakes up, Calypso is treating him.
• I Gave My Word: An oath on the River Styx is magically binding. Unless you are a god.
  • Gods are supposed to be bound by it as well, and breaking it causes them to be exiled from Olympus for a decade without receiving any divine food. Of course, Zeus being the god in charge of enforcing oaths and not exactly a great role model, he decided to not enforce the consequences on himself. The same goes with Poseidon.
  • In fact, a promise is not binding unless sworn on the River Styx, something taken advantage of several times in the series.
• "I Know You Are in There Somewhere" Fight: Annabeth to Luke in The Last Olympian.
• I Need to Go Iron My Dog: The Battle of the Labyrinth gives us this gem of an exit line from Tyson:
  Tyson: I need to go... um... polish my fish ponies.
• Incest Standards Are Relative: Percy mentions that since the gods don’t have DNA, the Divine Incest prevalent in Classical Mythology is considered acceptable. This means relationships between campers are accepted, and even prevalent. There is one taboo, though—it’s not acceptable for campers to date someone from their own house (meaning they share a divine parent).
• Inferred Survival: Even after the climax, it's revealed that Kronos is still out there somewhere, as he is immortal and cannot die. It is said that Kronos might be scattered so thin across the world that he might not be able to form a consciousness again, but what would be the fun in that coming true?
• Informed Poverty: Percy says that him and his mother are poor, with a rental movie and takeout from cheap fast food place such as Burger King being a once-in-a-while, special occasion-type outing because of the cost. Yet he goes to a private school and is implied to have done so since first grade. He takes not a bus or the subway home, but a taxi. They can afford to own their own apartment. By all means, it might be stated that the Jacksons are poor, but what is shown suggests that they are at least middle class.
• Innocently Insensitive: Perdix, it is not a good idea to ask your uncle Daedalus if his son died flying because the wings he made him failed.
  • Nico also asks why Annabeth didn't know better than to fall off a cliff to save him and his sister, seeing as she's the daughter of the goddess of wisdom. Ouch.
• Internal Reveal: As Percy states in the first paragraph of the series, he's a halfblood. However, it takes a decent amount of time for Percy in the story to learn this (and, subsequently, that Greek mythology is real).
• Interspecies Romance: Where would a series based on Greek mythology be without it?
• In Which a Trope Is Described: Every chapter likes to explain exactly what happens in said chapter, usually in sarcastic and witty ways: "I Accidentally Vaporize My Pre-Algebra Teacher", "A God Buys Us Cheeseburgers", "Grover Buys a Wedding Dress", "Pigs Fly"...
• Island of Mystery: The island of Ogygia, Calypso's home/prison, which cannot be reached by any normal means. The Fates only allow heroes that Calypso can't help but fall in love with to wash up there, but eventually they all go, leaving her alone once again. It plays a further role in The Heroes of Olympus.
• It's Personal with the Dragon: Since Kronos spends much of the series as a disembodied voice, Percy spends most of his time fighting Luke, Kronos' Dragon who serves as The Heavy. Percy develops a personal beef with Luke both because he betrayed Camp Half-Blood, and because Annabeth seems to have feelings for him.
• It Was a Gift: Good gifts, cursed gifts, it's all good.

J

• Jedi Mind Trick: Or as we should call it here, manipulating the Mist. Thalia uses it in The Titan's Curse to trick Dr. Thorn and another teacher into thinking that she, Percy, and Annabeth are Westover students and not visitors on a rescue mission.
• Jerkass: Gabe Ugliano, who is both abusive and rude and plays poker with his sleazy friends. He gets his comeuppance.
• Jerk Jock: The Ares cabin in general, and Clarisse in particular.
• Just Eat Gilligan: The crux of the series' entire plot is that the fate of Olympus may be changed once a halfblood of the eldest three gods reached sixteen. As Percy immediately asked when he learned about this, why don't one of the gods just kill him, as that'd be the safest option. Annabeth responds that he's right. She explains that the gods mainly refrain from killing Percy because they're still waiting to see what hero he'll turn out to be. Also, they're worried about offending Poseidon.
• Just Train Wrong: There are a couple of glaring instances when it comes to railroads being used in the stories:
  • For instance, in The Lightning Thief, Percy, Annabeth and Grover take an Amtrak train from New Jersey to Denver, Colorado — a one-seat ride that also goes through St. Louis (for the Echidna encounter in the Arch). There are several things that are extremely inaccurate with their journey:
    • A one seat ride from New Jersey to Denver via St. Louis is impossible. There are no coast-to-coast intercity trains in the United States. (The Sunset Limited used to run from Orlando to Los Angeles until August 2005 when Hurricane Katrina truncated the route to New Orleans.) Any intercity trains out of Penn Station only go as far as Chicago, requiring a change of trains there as well. Also, although Amtrak has trains to Denver and St. Louis, completely different trains reach these cities from Chicago — the Texas Eagle for St. Louis and the California Zephyr for Denver.
  • In The Titan's Curse, the heroes board an autorack freight train in Washington DC and wake up the next morning in Cloudcroft, New Mexico. It should be noted that the nearest railroad to Cloudcroft is in Alamogordo. Furthermore, it's impossible to travel the distance overnight, although it's also possible Apollo had something to do with speeding up the pace of the journey.

K

• Kid Hero: Just about every single Half-Blood in this book. However, it's deconstructed in that they tend to lead very rough lives due to what made them 'heroes' in the first place — they tend not to fit in with mortals due to their supernatural neurodiversity and often discriminated against because of this, and they live in fear of being attacked and killed by monsters that are attracted to their scent on the godly side. They're lucky to reach maturity and it's very rare for any of them to settle down and live a happy life outside of Camp.
• Killed Off for Real: Everyone who dies in the series. The only aversions to this are Luke who dies for real in The Last Olympian and Tyson. Everyone else thinks that Percy dies, too, but since the story is from his perspective and we know otherwise, it doesn't count.
• Kissing Cousins: Percy's father, Poseidon, is Annabeth's great-uncle, making the two of them first cousins once removed. However, considering the giant amount of incest that is Greek mythology, this doesn't come up at all.
  • All the incest in Greek mythology is eventually explained in-series by the idea that the gods have no DNA and therefore cannot inbreed the way humans do. Demigods at Camp Half-Blood feel free to date any fellow demigod who does not share a divine parent — in other words, two Athena kids (half-siblings) would not go out, but an Athena kid and a Poseidon kid might, regardless of their technical relationship.
• "Kiss the Cook" Apron: In The Battle of the Labyrinth, Geryon wears three aprons, one on each of his bodies, with one word of the phrase on each.

L

• The Lad-ette: Clarisse. She is Ares' daughter, after all.
• Landmarking the Hidden Base:
  • Mount Olympus is reachable via a special elevator to the 600th floor of the Empire State Building.
  • Alcatraz contains an entrance to the Labyrinth.
• Lamarck Was Right: The Big Three weren't born rulers of their domains; they divided the world up after defeating their father. In addition, gods apparently don't have DNA. As such, the heroes inheriting some of their parent's powers, especially when it comes to children of the Big Three, is an example of this. Of course, the question of divinity confuses things in general.
• Laugh of Love: In The Last Olympian, Annabeth laughs right before she has her first kiss with Percy.
• Leeroy Jenkins: Percy has a tendency to recklessly charge into battle without a proper strategy.
• Let's Get Dangerous!: In The Last Olympian, it's calm, quiet Sally Jackson and Paul Blofis. Who thought that two humans, one of whom can't even see through the Mist, could kick so much monster butt?
  • Mr. Chase gets a moment when he manages to kill a large number of the Titan's army using an antique plane he outfitted with an automatic gun that fires Celestial Bronze bullets. He has one of the highest kill counts in the series.
• Libation for the Dead: Nico must offer food and drink to consult spirits. One chapter in Battle of the Labyrinth is even titled "Nico Buys Happy Meals For The Dead." He typically uses French fries and coke.
  • Minos, his Treacherous Advisor, complains that it's traditional to use animal blood for necromancy. Nico tells him to shut up.
• "L" Is for "Dyslexia": All half-bloods are dyslexic since their brains are "hard-wired" to read Ancient Greek instead of English. As a result, reading even regular signage is difficult unless it's in very large font.
• Liminal Being: In The Sea of Monsters, Chiron observes that half-god and half-human heroes exist on two levels, as other creatures with mixed divine and other heritage do not.
  But you, Percy — you are part god, part human. You live in both worlds. You can be harmed by both, and you can affect both. That's what makes heroes so special. You carry the hopes of humanity into the realm of the eternal. Monsters never die... They must be defeated again and again, kept at bay. Heroes embody that struggle. You fight the battles humanity must win, every generation, in order to stay human.
• Living Labyrinth: Daedalus' Labyrinth grows over time. It's grown enough to apparently develop Roman elements.
• Load-Bearing Hero: Percy and Annabeth both pull this one, except they're holding up the sky, technically making them load-bearing heroes for the entire planet.
• Locked into Strangeness: Percy and Annabeth get matching gray streaks in their hair after holding up the weight of the sky in The Titan's Curse.
• Locked Out of the Loop: Percy, for much of the series. It's a bit downplayed, as only Chiron and Annabeth are really in the loop in the first place.
• Lotus-Eater Machine: The Lotus Hotel and Casino, named after the Trope Namer. Time speeds up significantly. Two weeks in that hotel equal 28 years in the real world, and one hour is the equivalent of five days.
• Lovable Rogue: Hermes, as in mythology — and by extension, most of his demigod children. Luke is a subversion.
• Loved Ones Montage: Percy gets one when he bathes in the Styx. It's the thought of Annabeth that finally gets through to him.

M

• Mad Oracle: May Castellan goes insane when she tries to become the Oracle of Delphi.
• Made of Iron: Luke and Percy, having both bathed in the Styx. And Achilles and the Nemean Lion.
• Magic Compass: In The Demigod Files short story "The Sword of Hades", Percy, Thalia and Nico are given a flower by Persephone that will point to the direction the thief who stole the titular sword is in. It loses petals the closer the thief gets to escaping.
  • The thermos that Hermes gives Percy in Sea of Monsters could arguably be called a compass, as while its main purpose is to hold winds of the four cardinal directions, the lid can also be used as a compass, as the part that points to the North will be the coldest and the part that points to the South will be the hottest.
• Magic Map: When Percy Jackson goes to the undersea kingdom, there is a mosaic in the palace there that forms a map of the battle taking place, with colored tiles that move around on their own for the different forces.
• Magical Negro: When Apollo briefly appears as a homeless man.
• Magic Pants: At the end of the Sea of Monsters, when the Golden Fleece heals Thalia it leaves her appearing as a teenager (her current chronological age), although she was much younger when she was mortally wounded and turned into a tree. Thankfully, the clothes she was wearing are also adjusted so that they still fit.
• Many-Faced Divinity: Several Classical Mythology gods reprise their multi-faced appearance here, particularly Janus.
• Apple of Discord: Hilariously used by the Stoll brothers to pull a prank on the Aphrodite cabin in The Demigod Files.
• Marked to Die: Zoe realized from the beginning who the one meant to die by a parent's hand was.
• The Marvelous Deer: In the The Demigod Files short story "The Sword of Hades", Thalia is led to meet Percy and Nico by the Golden Hind, which is, in fact, literally gold.
• Masquerading As the Unseen: Annabeth distracts Polythemus from her friends by donning her invisibility hat and saying she's Nobody, an alias Odysseus used to outsmart the cyclops in ancient times. It works, but then she gets caught, so Percy hides from view and does the same thing.
• Matter of Life and Death: Spoken by Rachel to convince her father that Percy is in danger.
• Meaningful Name: Many of the more minor half-bloods have names which reflect their divine parent:
  • Hephaestus has a kid whose last name is Mason, Apollo has sons whose last names are Yew and Fletcher...
  • Riordan didn't bother with some of the minor half-bloods, but the worst offender has to be Demeter's daughter. Demeter is the goddess of grain, fertility, and harvesting. One of her daughters is Katie Gardner. Not only that, but one of her other daughters is Miranda Gardiner.
  • Don't forget Connor and Travis Stoll. The sons of Hermes, god of thieves. Percy even points this one out since it's so obvious. It might be interesting to point out that Connor and Travis Stoll are real brothers who at one point were in Riordan's class. Charles Beckendorf, albeit with a different appearence, was also a student.
  • Silena Beauregard's (daughter of Aphrodite) surname comes with a helping of Bilingual Bonus as it means "beautiful gaze" in French.
  • A rather tragic example: 'Zoe' means "life" in Greek. And her surname is 'Nightshade'. Nightshade is another name for a family of poisonous plants. How did Zoe die again? Oh yeah, poison was a part of it!
  • Grover, who has a big fixation on nature (he's a satyr, it's his job), has "grove" in his name as well as the surname, Underwood.
  • Also Rachel Elizabeth Dare, in a Steven Ulysses Perhero-ish way. And boy, does Rick Riordan feel proud of that particular idea. Her initials are RED and she has red hair. Probably coincidental.
  • People might not necessarily remember Mrs. O'Leary, but they sure remember the lantern her cow kicked over.
  • Percy, twice over. In-Universe, his mother named him Perseus in the hopes that it would be good luck — he was one of the only Greek heroes to get a happy ending. And from a real-world perspective, the name roughly translates to "the destroyer" in Greek. Highly appropriate for a potential Apocalypse Maiden with major destructive power.
  • Luke's another layered one. The name means "light" or "light-bringer", but in a Light Is Not Good fashion, as it's taken from Lucifer, fitting for a paragonic rebel who tries to destroy the gods themselves. The nicer connotations foreshadow his ultimate redemption and role in saving Olympus.
  • Thalia Grace: The Charites, also known as Graces, are three daughters of Zeus in Greek mythology, often associated with charm, beauty, and goodwill. One of them is named Thalia
    • Inverted meaningfully for Thalia: The Graces are often associated with Aphrodite, mainly by Homer, but Thalia joins the immortal Hunters of Artemis, remaining forever 16 and a maiden
• Mega Neko: The Nemean Lion.
• Monstrous Seal: The Telekhines are literal monsters that are often compared to seals in appearance.
• Monumental Battle: The Gateway Arch in the first book.
• Monumental Damage:
  • Again, the Gateway Arch. The Chimera burns a hole in it.
    "Great, we just blowtorched a national monument."
  • The Air & Space Museum in The Titan's Curse due to a Nemean Lion attack (which will certainly put the Secret Service and FBI on high alert), and a lot of trouble at Alcatraz in the fourth (with Kampe and Briares).
  • Not to mention the damage done to Manhattan in the last book.
• More Hero than Thou:
  • Grover and Annabeth arguing over who should stay behind in the Underworld so that Percy can save his mom.
  • Played with in The Titan's Curse. Percy had no problem with going head-to-head with Atlas. It wasn't until Ares' curse kicked in and sapped Percy's sword skills that he even tries to take the sky. Then Percy practically pleads for Artemis to let him hold up the sky for her because she could fight better than he could.
• Muggle and Magical Love Triangle: Percy has a choice between Annabeth, a fellow half-blood hero, and Rachel, a mortal. It's played with to some extent, since Rachel has the rare ability to see through the Mist. She also eventually becomes Camp Half-Blood's new Oracle, but it was only after the triangle essentially disappears when she "dumps" Percy following her realization that she was only attracted to him because of her destiny of becoming the Oracle.
• Multiple-Choice Chosen: Initially, there's only one candidate for The Chosen One specified in the Great Prophecy, Percy Jackson (since it necessitates a demigod child of either Hades, Zeus, or Poseidon to reach their Dangerous 16th Birthday, and he's the only one they know about). However, more candidates appear in later books - other demigod kids of those three gods born earlier and have had their aging halted by extraneous circumstances - and the gods attempt to manipulate which one the chosen one will be to suit their own ends.
• A Mythology Is True: The Greek myths are true. Christian myth is in the territory of "Maybe yes, maybe no, let's not talk about it". Roman, Egyptian, and Norse myths are also true, and they all exist in the same universe.

N

• Named Weapons: Anaklusmos/Riptide (Percy's pen-sword) and Backbiter (Luke's sword).
  • Backfired on Clarisse with "Maimer" (her electric spear), which all the campers mockingly call "Lamer".
• Names to Run Away from Really Fast: Kronos is called "the crooked one" in The Lightning Thief in reference to his tendency to lie and manipulate. Percy himself, in a way (see Meaningful Name for details).
• Narrative Profanity Filter: Both English and Ancient Greek.
• Nature Spirit: The nymphs and dryads.
• Nemesis Weapon: Luke creates a special sword called Backbiter, which has one blade made of Celestial bronze (which can harm monsters, immortals, and heroes, but can't harm mortals) and one blade made out of tempered steel (which can't harm monsters and immortals, but can harm heroes and mortals). This serves as an antithesis to all heroic weapons, which are only forged out of celestial bronze as heroes are never supposed to harm mortals, but more specifically it works as an antithesis to Percy's Riptide.
• Neurodiversity Is Supernatural: Demigodhood causes dyslexia and ADHD. Justified as demigod brains being hardwired to read only Ancient Greek and having overactive natural battle reflexes.
• Never Found the Body:
  • One of the Titans or other was a disembodied soul and we never saw him or her die. Or something.
  • A truer example: Bianca's body was never recovered, nor is Michael Yew's.
• Nice Job Breaking It, Herod: Kind of. By killing Maria di Angelo in an attempt to kill Nico and Bianca, Zeus gave Nico a reason to hate and want to destroy the gods, which is what Zeus was trying to prevent in the first place. Luckily, Nico didn't act on it. But Hades, in anger at his mistress being killed, cursed the Oracle so that she would remain the Oracle forever, whereas normally the power changes bodies every few decades. The curse preventing the transfer to Luke’s mom drives her mad when he’s a baby, and Luke feels left alone and resents his parents as a result.
• Nice to the Waiter: Hestia, in the form of a young girl, says that almost no one (including Percy) ever stops to speak with her. Nico di Angelo is one of the exceptions.
• No Eye in Magic: Percy, Grover and Annabeth encounter the actual Medusa from Greek Myth. Percy sees her through a glass gazing ball, so he doesn't get Petrified.
• Noodle Incident:
  • One of the key events of a year at Camp Half-Blood prior to the series involves a centaur in a prom dress.
    Annabeth: Now that was a weird summer.
  • In The Last Olympian, when Percy arrives at Camp Half-Blood:
    Our beach is on the North Shore of Long Island, and it's enchanted so most people can't even see it. People don't just appear on the beach unless they're demigods, or gods, or really, really lost pizza delivery guys. (It's happened — but that's another story).
  • This line from The Sword of Hades:
    Nico: (to Persephone) Family spat? You turned me into a dandelion!
  • This is sometimes used in an individual book to refer to events that happened in previous ones without giving the details away. For example, from Battle Of The Labyrinth, in a conversation between Percy and his mom:
    "I told them you were all right," my mom said, but she sounded like the weight of the sky had just been lifted off her shoulders — and believe me, I know firsthand how that feels.
  • In The Titan's Curse, it's said that the Hunters didn't have a very cordial encounter the last time they were at Camp Half-Blood. Including the fact that they burned down a few cabins.
• No Matter How Much I Beg: In The Sea of Monsters, Annabeth wants to hear the Sirens but doesn't want to get killed. She then asks Percy to tie her up and never let her go, so Percy fills his ears with wax so he can't hear the Sirens or her pleas. Unfortunately, she still has her knife, so she eventually escapes. Percy comes after her and manages to grab her before she could drown. Also, he realizes that she can't hear them underwater, so he creates a giant air bubble for them to stay in until the song is over.
• No One Could Survive That!: Luke's 50-foot fall in The Titan's Curse, which, of course he did survive.
• Normally, I Would Be Dead Now: Played so straight it hurts. But for Percy, anything with water is justified because he's the son of the sea god.
• Not a Date: Percy insists that his planned afternoon with Annabeth at the start of Battle of the Labyrinth is not a date, though his mom thinks otherwise.
• The Nothing After Death: The Fields of Asphodel (the same one from Greek mythology), the most widely populated part of the Underworld.
  Grover: Imagine standing in a wheat field in Kansas. Forever.
• Nothing Is the Same Anymore: The Minotaur's capture of Sally is the exact moment that changes Percy's life forever, leading to a new life of hardship, followed by the training and quests he must take to save the planet.
• Now or Never Kiss: In The Battle of the Labyrinth, when Percy and Annabeth are infiltrating the Titan base in Mount St. Helens, Percy tells Annabeth to leave and tell Hephaestus and Camp Half-Blood what they found. Thinking he might be about to die, she kisses him for the first time. By the time he makes it back to camp, he arrives just as they're having his funeral.

O

• Obliviously Superpowered:
  • Before demigods know of their godly heritage, they already have supernaturally enhanced battle reflexes and an ability to read divine Ancient Greek, often diagnosed as ADHD and dyslexia by mortals. They may also get prophetic dreams.
  • Certain demigod children also manifest other unconscious abilities, depending on their godly parent. Percy, son of Poseidon, displays unconscious hydrokinesis twice in The Lightning Thief, once against Nancy Bobofit and once against Clarisse during Capture the Flag, not realizing he caused it until he was claimed by Poseidon.
• Offerings to the Gods: At dinner, campers at Camp Half-Blood toss a bit of their food into a fire in the middle of the picnic area to send to their parents. Traditionally, they use the most delicious part of their meal, like the biggest strawberry or the most buttery roll.
• Official Couple: By the end of the series, we have Percy and Annabeth, Clarisse and Chris, and Grover and Juniper, among others.
• Offing the Offspring: In The Titan's Curse: "one shall fall by a parent's hand". (It was Zoe Nightshade.)
• Oh, My Gods!:
  • Done since it's, well, y'know... Either that, or "di immortales", which is the same, but Latin.
    Dionysus: Zeus knows how many more.
    (lightning rumbles)
    Dionysus: Strike that. Even Zeus doesn't know.
  • Percy plays with this in Percy Jackson's Greek Gods. When he's narrating the stories about the Olympians, he has them say things like "Holy me!"
  • Different characters have different variations. "Gods of Olympus" and (in The Heroes of Olympus) "Gods of Rome" are popular. Nico di Angelo has his own particular variation; he tends to use "Styx!" as an exclamation or in place of "gods".
• One-Winged Angel: Subverted. Kronos is defeated before he can show his true form and make his enemies despair.
  • Ares does pull one at the end of The Lightning Thief, but only after already losing the fight from getting stabbed in the heel. He was about to kill Percy for sure when Kronos evidently changed his mind, and he settled for cursing Percy and going somewhere to heal instead, turning into his full divine form to warp somewhere else. But looking at it would have killed Percy.
• Only I Can Kill Him: Luke towards Kronos. Only he knows his weak spot and thus can effectively commit suicide and take Kronos with him.
• Our Dragons Are Different: Dragons and drakons are distinct, albeit similar, creatures. Dragons are by and large the typical fantasy kind, winged and fire-breathing and sometimes used as guardian animals - one is used as a perimeter guard at Camp Half-Blood, for instance. Drakons are much bigger, much more dangerous beasts and have no wings; many have no legs either, and, like Greek mythical dragons, they are essentially really big snakes.
• Our Hippocamps Are Different: The hippocamps in the series are a fairly traditional take on the mythological kind and are most often seen as servants and emissaries of Poseidon. The hippocamp Rainbow is a major recurring ally and the associated mount of Tyson.
• Our Hydras Are Different: A hydra appears in The Sea of Monsters as a beast recently spawned from a Monster Donut shop; it grows two heads for every one lost as per standard, and the severed heads themselves will seemingly regrow into Monster Donut shops elsewhere.
• Our Nymphs Are Different: Nymphs of various sorts appear fairly often as minor Nature Spirits and supporting characters. A large population of dryads inhabits Camp Half-Blood's forest alongside the satyrs, while naiads live in its lake. Other naiads appear, inhabiting rivers throughout the series, including the Mississippi. Nereids are part of Poseidon's court, and while naiads do not serve him directly they still honor him.
• Outgrown Such Silly Superstitions: Percy attempts to tell Dionysus this, but he is promptly set straight. Dionysus explains how people from all times laugh at the lack of knowledge the past had, and how in the future people would be laughing at people of Percy's time for what they didn't know.
• Overly Long Gag: In The Titan's Curse - the entire DAM(N) sequence.

P

• Paper-Thin Disguise: Silena leading the Ares cabin to battle in The Last Olympian. Even lampshaded by Clarisse.
  "Seriously, not one of you noticed?!"
• Parental Abandonment: Every half-blood is abandoned by their immortal parents and gets occasional visits if they're lucky. Lots of half-bloods never even learn who their divine parent is.
  • Also averted by mortal parents like Sally Jackson and Paul Blofis as well as Annabeth's parents.
  • Not so averted by Luke's mom May. She's there, but she ain't there. Thalia's mortal mom doesn't sound like she would have won any parenting awards either, not even when she was alive.
• Parental Favoritism: Greek gods are genetically guilty of this.
  • Poseidon openly admits that Percy is his favorite son. That in itself becomes something of a invokedHarsher in Hindsight moment when Triton appears in The Last Olympian and is clearly jealous of Percy.
• Perky Goth: Nico (well, before Bianca's death sends him slightly off the deep end) and Thaila.
• Pet the Dog:
  • Dionysus, who is quite a grouch and always seems happy to put Percy and his friends down, helps Grover out in The Battle of the Labyrinth, supporting him when he announced that the god Pan was dead. He also showed genuine grief for his son Castor when he died, and helped cure half-blood Chris Rodriguez who had previously gone insane. It's also subtly implied that he's a lot more pleasant when he's around his wife, whom he genuinely loves.
  • Ares gets one as well, when he gives a So Proud of You line to his daughter Clarisse. Which is made sweeter and/or kinda sad when it's been made pretty clear that he's literally abusive and Clarisse was still worried she'd get hit or blamed somehow.
• Physical God: The Greek gods and their various relatives are very real, very physical people.
• The Plan: Kronos pulls off quite a few.
• Powered by a Forsaken Child: Percy speculates that someone has been killed to make Luke's sword.
• The Power of Friendship: In The Last Olympian, the Ares cabin followed Silena not because they didn't guess it wasn't Clarisse, it was because they wanted to fight next to their friends.
• Power Trio: Typical for anything Greek, since three is a sacred number. So many examples, but here's just a few:
  • Obviously, the Big Three: Zeus, Poseidon, and Hades.
  • Then there are their kids, Thalia, Percy, and Nico. (They start off numbering four, but Bianca gets offed fairly quickly and before her parentage is even known.)
  • Thalia, Luke, and Annabeth.
  • It's a camp rule that any hero who sets out on a quest is allowed to take two and only two companions, specifically because three is a good number. The rule is broken twice: the five questers (Zoe;, Bianca, Thalia, Grover, and Percy) in The Titan's Curse and the four (Annabeth, Percy, Tyson, and Grover) in The Battle of the Labyrinth. The consequences of breaking this rule are sometimes disastrous.
  • The most obvious one: Percy, Annabeth, and Grover. They're the three main ones for most of the series and are really close.
• Prophecies Are Always Right: Every prophecy comes true.
• Prophecy Twist: One in every book. In fact, it wouldn't be Percy Jackson and the Olympians without 'em.
• Psychic Dreams for Everyone: Well, almost everyone. How nifty.
  • It's even lampshaded. During a war, Percy and another half-blood have an exchange about how they need to sleep but really don't want to. Percy, in narration, explains that demigods' dreams suck, since they're frequently visions and prophecies and other psychic junk which isn't fun at all, and the more tense things are, the worse the dreams are. For a while, Percy even had Kronos showing up in his dreams to taunt him (and Kronos is good at it, too).
• Pun: Percy is able to sneak these by people who are more familiar with Greek mythology. A shining example from The Battle of the Labyrinth:
  "Red cattle. The cattle of the sun. They're sacred to Apollo."
  "Holy cows?"
  "Exactly. But what are they doing —"
• Put on a Bus: Thalia, the Hunters, Chris. The implication is that they're off having adventures, just like Percy and his friends.

Q

• Quest to the West: The prophecy given before the quest in the first book starts with "You shall go west, and face the god who has turned".

R

• Real Event, Fictional Cause: It's revealed that World War II was basically a case of the children of Zeus and Poseidon (part of the Allies) fighting against the children of Hades (part of the Axis). This was actually the reason that Zeus, Poseidon and Hades agreed not to have any more children, as they were too powerful. Zeus and Poseidon violated their agreement, however.
• Really 700 Years Old: All the gods, plus several demigods.
• Recycled In Space: Although it's done well in this case. Many of the plots or subplots are the major arcs of well-known Greek myths. The Sea of Monsters is Jason and the Argonauts and the Odyssey stuck together. Silena's fight against the monster in the final book and Clarisse's subsequent beatdown of the monster that killed her is Patroclus stealing Achilles' armor and Achilles' fight with Hector, complete with dragging the corpse around behind her chariot. Riordan is quite clever in working the myths into his books.
  • This is justified in the The Last Olympian, when Prometheus says that patterns repeat themselves in the world.
  • This also comes up in The Kane Chronicles, where the reason gods want mortal hosts is that they can change those patterns.
• Redemption Equals Death: Daedalus in The Battle of the Labyrinth; and Silena, Ethan, and Luke in The Last Olympian.
• Red Herring: The entire series builds up to Percy and his role in the Great Prophecy. Kronos' army and the Olympians obsess over what to do with him, and whether he'll develop into the savior or destroyer of Olympus when he reaches his impermissible sixteenth birthday. Two more possible candidates for the half-blood of the prophecy are also introduced (Thalia and Nico), meddling the possible outcome further. So, when the battle of the Second Titan War finally comes, what role does Percy play as the forbidden demigod? In a direct sense, nothing. The "hero" the prophecy described that would end the war actually turns out to be a different person. The motivation as to why the war even happened ultimately had nothing to do with Percy, with him instead always just being a means to an end. And, all in all, the prophecy being fulfilled on Percy's sixteenth birthday had nothing to do with anything. In the grand scheme of things, the fact that the preservation or destruction of Olympus would occur the next time a half-blood of the eldest three gods turned sixteen was more or less a random tidbit the Oracle decided to use to mark the date, considering the fact that it wouldn't happen for quite some time. And to top it all off, the only reason a half-blood child of those gods wouldn't turn sixteen for such a long time was solely because of the prophecy in the first place!
• Reformed, but Rejected: Nico di Angelo, until the very end.
• Refusal of the Call: Played straight and played with in The Titan's Curse:
  • Played straight when Thalia joins the Hunters to avoid turning 16, thus having The Great Prophecy not affect her.
  • Played with in the case of Bianca, who was completely in the running for being The Chosen One, other than the fact that she decided to join the Hunters long before anyone knew that she was a daughter of Hades.
• Refusing Paradise: Percy refuses the offer to become lieutenant to his father Poseidon and gain eternal immortality. He refuses it on the grounds that he's about to enter high school and he doesn't want to lose the possibilities his regular life gives him, but it's heavily implied it's so he can stay with Annabeth.
• Religion of Evil: Subverted and discussed. Antaeus kills anyone who stumbles into his lair and dedicates their skulls to his divine father... Poseidon, also father to The Hero Percy. The whole thing disturbs Percy, who confronts his pop about it later on; Poseidon, clearly uncomfortable, explains that while he can't play favorites when it comes to his kids, he doesn't necessarily approve of everything they do in his name.
• Remember the New Guy?: Connor and Travis Stoll aren't mentioned until "The Sea of Monsters", but Percy claims he meet them during the event of the first book, back when he was living in the Hermes cabin during his time as unclaimed camper.
• Revenge by Proxy: A large part of the reason WHY so many monsters, beings, and gods attack demigods, is to punish the parents of those gods.
• Rhymes on a Dime: In The Last Olympian: "Curse me, eh, I'll make you pay! / I don't want to rhyme all day!"
• Riddling Sphinx: When Percy, Annabeth, Grover and Tyson meet a sphinx in the Labyrinth in Battle of the Labyrinth, it tries to administer a multiple-choice standardized test with mundane trivia questions (in the style of a game show with regards to her tone of voice, and the use of recorded applause from hidden speakers). Annabeth, who was expecting a riddle that would test her cleverness, is not amused.
  • Rick Riordan lives in San Antonio, Texas, and wrote the scene as a jab at the TAKS, the standardized test of Texas's grade schools at the time of publishing, with the Sphinx's instructions being word for word what the script teachers have to recite down to the instructions given on properly bubbling in the answers.
• Romantic False Lead: Luke is one for Annabeth, while Rachel is one for Percy.
• Rule of Cool: The existence of the Athena cabin. This goes against all traditional mythology, as Athena was a virgin goddess. Downplayed in the sense that an In-Universe explanation is given as to how Athena can have kids and still be a virgin. However, Riordan has admitted the real reason she can conceive is because the idea of a demigod child of Athena was too cool to not include.
• Running Gag: Characters cursing in Ancient Greek, or "I said something really intelligent like..."

S

• Sapping the Shapeshifter: In The Titan's Curse, Percy seeks out Nereus for information on the monster that Artemis has been hunting, and it's not long before he's forced to wrestle the answers out of the old sea god as per the original myths. Nereus attempts to shake Percy off by diving into the ocean and transforming into a seal, a killer whale, and even an eel, but unknown to him, he's up against the son of Poseidon, and Percy's Super Not-Drowning Skills mean that Nereus soon tires himself out and is forced to submit.
• Scales of Justice: Ethan Nakamura's burial shroud has a set of scales on it. This is because Nemesis is his mother.
• Scenery Dissonance: The Type 1 version is brought up in The Lightning Thief. When his mother apparently dies, Percy reflects that it doesn't seem fair for the weather to be so nice and the scenery so idyllic. He feels like everything should be cold and grey.
• Science Is Wrong: Among other things, the seasons are caused by Persephone moving between the Underworld and Olympus, not the Earth's tilt, and global warming is simply Zeus being ornery. However, it's implied that there might be a combination of both, as the moon and sun clearly exist as physical forms, not controlled by Apollo and Artemis.
  • A later book series plays with this, establishing that science exists alongside the gods (at least in regards to the sun and moon) in the Riordanverse, explaining why gods can go missing and the world can still work.
• The Scottish Trope: Saying "The Furies" or the names of any god or Titan causes thunder to rumble (and apparently, gives power to that god/Titan). Even when there aren't any rain clouds around. At least once or twice in The Lightning Thief, Grover is about to refer to the Furies by name, but changes midway through saying it to say "Kindly Ones".
• Sea Monster: A wide variety of horrible things lives in the oceans, including Sea Serpents, centipede-like scolopendras, giant squid, telekhines and so on.
• Sea Serpents: A random sea serpent appears in "Percy Jackson and the Stolen Chariot" from The Demigod Files.
• Self-Fulfilling Prophecy: Zeus killed Maria di Angelo in order to prevent more Big Three children being born so that Kronos won't try to take over the universe. Hades, in anger at his mistress being killed, cursed the Oracle to be stuck in one body forever, when it’s meant to transfer to a new host every few decades. He then didn’t tell anyone about the curse, so no one stopped Luke’s mother from trying to take what should have been her position and being driven mad from the failed transfer of power. Being raised from infancy by one parent who is not all there and another who does the bare minimum to keep them both alive, Luke feels left alone and resents his parents as a result. Kronos uses this as an opportunity to manipulate Luke into helping him rise. Zeus just caused the prophecy to take place in the worst way possible.
  • That is the beauty of it. You Can't Fight Fate: the only way to not fulfill a prophecy is to simply not hear it, because once you do, it will happen. And another thing, Chiron points out that prophecies often have double-meaning, so the truth is not always clear until they actually come to pass and shouldn't be dwelled on too much.
• Semi-Divine: Most of the main characters are demigods with some form of supernatural powers.
• Sequel Hook: The prophecy at the end of The Last Olympian, which leads to...
• Sequel Series: Two, The Heroes of Olympus and The Trials of Apollo.
• Serious Business: The children of Aphrodite get more involved in capture-the-flag in The Titan's Curse when the Hunters of Artemis are at camp.
• Shadow Walker:
  • Nico di Angelo is able to "shadow travel" because he's the son of Hades. He claims that every shadow is one and the same, but he can only do it a couple of times a day (or preferably at night). It also drains him a lot to the point that the first time he used it, he passed out for a whole week.
  • Mrs. O'Leary, like all hellhounds, can do this.
• Shipper on Deck: Aphrodite is a big Percy/Annabeth shipper. Though (understandably) she thinks life is a soap opera (Lampshaded by her beau, Ares), and so assures Percy that she won't let things be easy for them (unintentionally lampshaded by Annabeth herself at the end), with plenty of invokedWangst, indecision, etc.
• Ship Tease:
  • Thalia/Luke. Two best friends who ran away together for roughly three years. Then Luke joining the Titans because one of his reasons was because of her death. The Titan's Curse also has a lot of moments where you find out that Thalia once considered joining the Hunters, but did not want to because she would be away from Luke. Then there was their final battle in The Titan's Curse which implied quite a bit.
  • Also, Annabeth/Luke. It started out as a crush on Annabeth's side. Annabeth also defends Luke many, many times in the books. In The Last Olympian, Thalia said that Annabeth always saw Luke as her hero.
  • And there are so many Percy/Annabeth moments that it could make a shipper faint.
• Ship Sinking:
  • Thalia/Luke by the end of The Titan's Curse, due to Thalia's Vow of Celibacy upon joining the Hunters. Good luck, shippers.
  • The Percy/Rachel ship is also sunk in the latter half of The Last Olympian before Percy gets together with Annabeth. Rachel realizes that her attraction to Percy was largely due to her destiny of becoming the next Oracle of Delphi and, in Percy's words, "dumps" him. Percy ends up feeling slightly dejected by this (his feelings for Annabeth notwithstanding), even though they weren't really dating to begin with.
• Shout-Out:
  • Too many shout outs to Classical Mythology to list. This is in part because author Rick Riordan is also a Greek researcher.
  • The Empire State Building's guard with the special 600th floor card for Mount Olympus apparently keeps up with trends in young adult literature.
    • In The Lightning Thief, he is reading a huge book with a picture of a wizard on the front. One guess who this "wizard" might be.
    • In The Last Olympian, he is seen reading a big black book with a flower on the cover.
  • Nico di Angelo owns a Mythomagic card deck, a reference to card games such as Magic: The Gathering. This is now invokedHilarious in Hindsight; Magic's Theros set is based on Greek mythology.
  • Nico references Spidey in The Last Olympian after taking Percy shadow-traveling on Mrs. O'Leary: "With great power...comes great need to take a nap."
  • A son of Apollo called Will appears in The Last Olympian and plays a minor (but not insignificant) role. Will's name is a shout-out to a certain playwright and poet who was said to also be a son of Apollo in-universe.
  • A freakish amount of products are also mentioned throughout the books. Burger King, Coca-Cola, Oreo Double Stuf cookies, even Lunchables... And that just scratches the surface. An exception, however, comes in the form of the Monster Donut chain.
    • In The Battle of the Labyrinth, Nico uses McDonald's Happy Meals to summon the dead spirits in one scene. One ghost even complains when he isn't allowed to get the toy!
• Shown Their Work:
  • There are many references to the Iliad and the Odyssey. If there's a place described that exists in real life you can recognize it from descriptions. Even epithets are alluded to (grey-eyed Athena, for instance). Riordan has clearly read the Theogony, the Iliad, the Odyssey, and a number of other minor books including Ovid's Metamorphoses. It shows up with bits like Apollo mentioning he really hates it when girls get turned into trees, or a thermos that perfectly mimics Odysseus' bag of winds. Medusa and several of the other monsters seem to be the only exception to this.^note It was not eye contact with her that turned you to stone but her entire face, and it was never made clear if she was really evil or not.
  • Rick Riordan had been an editor of mythology books in the past - and it shows. He even brings other elements, such as Roman aspects, into The Heroes of Olympus.
  • The ophiotaurus. It's actually part of Classical Mythology and is mentioned in one book. Exactly one book, until Riordan came along.
• Snicket Warning Label: Percy warns you that you should immediately put the book down if any of the descriptions of a demigod sound familiar to you, because if you figure it out, monsters will find you and probably kill you.
• Soft Water: Percy lampshades jumping from the St. Louis Arch in The Lightning Thief by saying that he is expecting the effect to be like hitting concrete when he strikes the water. But when he hits the water, he's perfectly fine and not injured in any way for a fall from a height that would certainly kill a normal person. Deliberately Justified because Percy is the son of Poseidon, so water cures him when it would have killed him.
• So Proud of You: Percy gets a lot of this from his father throughout the series.
• Spanner in the Works: Luke Castellan planned on delivering the Master Bolt and the Helm of Darkness to Kronos by sending Percy into the Crooked One's waiting clutches. To accomplish this, Luke gave Percy a pair of winged shoes that were cursed to drag him to his death once he was near Tartarus. However, Luke did not anticipate that Percy would be unwilling to wear the shoes, and giving them to Grover put a hitch in the entire plan. Of course, the heroes still reach the rim of Tartarus and just barely manage to escape before Kronos can drag them under, but they would had died if Percy had kept the shoes for himself.
• Spell My Name With An S: Canon example. The two first gods of earth and sky are Gaia/Gaea and Uranus/Ouranos.
• Stars Are Souls: The goddess Artemis's Lancer is killed. She is honored with a whole constellation.
• Starter Villain Stays: Percy's first major fight at the start of book one, the minotaur, returns in a later book - unfortunately for the monster, Villain Forgot to Level Grind and Percy dispatches it with much more ease the second time around.
• Stealth Pun: Plenty.
  • In The Lightning Thief, Percy, a son of Poseidon, mentions he's never gotten anything above a C- in his life. In other words, his grades are below C level.
  • Prior to the start of the series, Thalia was killed and her life force was converted into a pine tree that helped guard the border of the camp. She's made into a literal "barrier pine," a type of tree used to shelter houses from strong winds and storms.
  • In the fifth book, everyone in New York, "the city that never sleeps", has fallen asleep thanks to Morpheus.
• Steven Ulysses Perhero: Several demigod children, including Travis and Connor Stoll, the sons of Hermes, god of thieves, as well as Katie Gardner and Miranda Gardiner, both daughters of Demeter, goddess of agriculture. There's also Michael "Yew" (a type of wood often used to make bows) and Silena "Beauregard" (which translates to beautiful gaze), the children of Apollo and Aphrodite respectively.
• Succubi and Incubi: The empousai are a toned-down version, true to their role in Classical Mythology - they were one of the earliest forms of succubi. They're literal man-eaters who use a combination of flirtation, illusory beauty, and some sort of mind-scrambling lust magic to disarm their opponents. Their first appearance is in The Battle of the Labyrinth, when they attack Percy at his freshman orientation while disguised as cheerleading upperclassmen.
• Summon to Hand: Percy's sword Riptide is enchanted so that it always reappears in his pocket after a short time if it's separated from him.
• Superhero School: Camp Half-Blood teaches the children of gods stuff.
• Supernormal Bindings: When Artemis is captured in The Titan's Curse, she's briefly shackled before being forced to take Atlas' place holding up the sky.
• Super-Reflexes: This is given as the reason many of the demigods end up diagnosed with ADHD. There is a similar explanation of dyslexia being the result of having a brain hardwired for ancient Greek; both were written in for the benefit of Riordan's son Haley, who has both ADHD and dyslexia.
• Suspiciously Specific Denial: In the first book, Ares does this.
  Ares: "I am the god of war! I take orders from no one! I don't have dreams!"
  Percy: "Who said anything about dreams?"

T

• Take That!:
  • The Sphinx scene in Battle of the Labyrinth appears to be a jab at U.S. education when she tries to administer a standardized test to Annabeth:
  "Think? How am I supposed to test whether you can think?"
  • A much more blatant Take That! comes from Thalia in The Titan's Curse:
  "Ugh. Who picked the Jesse McCartney?"
  • Being forced to listen to opera music is one of the eternal tortures in the Fields of Punishment.
• Tasty Gold: During the Three Grays' taxi ride in The Sea of Monsters, Anger (the one sitting in the shotgun seat) asks Wasp (the driver) to give her Annabeth's coin so she can bite it.
• Theme Naming: Sometimes coinciding with with puns. Examples include Annabeth, daughter of Athena (and whose name contains 'Athena' plus a few extra letters) and Clarisse, daughter of Ares (same case). Other examples include Nico di Angelo, son of Hades and, possibly, Ethan Nakamura (whose surname is Japanese for "village in the middle", with respect to divided loyalties).
• Thicker Than Water:
  • Nico's argument to Hades in The Last Olympian: whatever the Olympians had done to each other, they were family.
  • Percy and Tyson deepen their bond by finding out they are half-brothers. Not that they get along with Poseidon's other sons.
    • It's played with, though. Tyson and Percy were already friends, it's just that finding out that one of your best friends is your brother and a cyclops makes things a bit... awkward between them. It doesn't help that Percy is teased relentlessly about it. Subverted when the Big Bad of that very book is Polyphemus, a fellow son of Poseidon, whom Tyson and Percy open a can of whoop-ass upon.
• Threads of Fate: In the first book, before Percy is aware of his Divine Parentage or the existence of the Olympian gods, he sees the Fates - who just look like three old ladies - sitting at a fruit stand and knitting a giant pair of electric-blue socks. The middle one cuts the yarn with a huge pair of gold and silver scissors, and the sound scares him for reasons he doesn't yet understand. In the last book, after the gods and demigods have defeated the Titans, and Luke has sacrificed himself to defeat Kronos, the Fates arrive to bear away his body and show Percy that same strand of blue yarn, representing his life that was cut short to save the world.
• Titanomachy, Round Two: The series has a plot that revolves around the attempts of Kronos to subvert and corrupt multiple demigods to free him from Tartarus. Kronos and the Titans (who are portrayed as human-like, save for being roughly ten feet tall and some having inhuman features like Hyperion having copper skin and flaming eyes) are actively working to free themselves and build an army using agents outside of Tartarus. On top of that, rather than just being a rampaging monster, Kronos is very much a thinking, scheming character and instead of breaking out the normal way, he possesses a demigod's body to hold his essence while he regenerates a new body, as his original was destroyed in the first Titanomachy.
• Time Master: Kronos is an evil example of this.
• Title Drop: This happens in pretty much every book:
  • In The Last Olympian, Hestia says: "I am here because when all else fails, when all the other mighty gods have gone to war, I am all that's left. Hearth. Home. I am the last Olympian."
  • Count how many times the titular Sea of Monsters is referred to by name in The Sea of Monsters.
• To Hell and Back: Percy has been to hell. Three times at least.
• Together in Death: Silena and Beckendorf.
• Too Dumb to Live:
  • Nearly everyone at times, but a particularly egregious example is when they enter Hephaestus' junkyard and after explicitly being told not to touch or take anything by another god, everyone does exactly that. Granted, they quickly wise up and put them back, and it's all but stated they would have gotten out since they didn't technically take anything out... but then Bianca decided it was a good idea to smuggle one little figurine out and then they had to fight a giant metal construct.
  • It's even worse for Grover. When told not to touch anything in the junkyard, his immediate response is to pick up a golden crown and bite a piece off! Guess his unconscious eating habits got the better of him.
• Took a Level in Badass:
  • Nico in The Titan's Curse after he realizes he is so much more awesome than he thought. In fact, not only is Nico much more powerful than he's initially implied to be; he goes from being an annoying little kid to one of the most deadly demigods alive in under a year. He's literally put himself through Training from Hell.
  • Percy, after taking a dive in the river Styx.
• Totally Radical:
  • Lots and lots of it, probably because it is told from the first-person narrative of a young teen, but actually written by a middle-aged man.
  • Intentionally used in-universe when Percy realizes the true nature of the Lotus Casino: the kid he's playing with uses old slang that is way out of date.
• Tragic Intangibility: Nico di Angelo manages to bring back the ghost of a departed loved one, only to find that their body is made of mist that disapates as soon as it nears living skin. Even as the ghost tries to console him in his grief, it can't even put a hand on his shoulder.
• Trapped in the Host: The Oracle of Delphi possesses young maidens as hosts. However, Hades laid a curse on the Oracle to be stuck inside the current body it was possessing even after that body died. In the present, the Oracle remains trapped inside the host's now long-dead and mummified body. Until The Last Olympian, when it is finally freed and Rachel becomes the new host.
• Troubled, but Cute:
  • Nico di Angelo, after the death of his sister Bianca.
  • Percy himself. On the very first page of The Lightning Thief he tells the reader he goes to Yancy Academy, a boarding school for "troubled kids", then "Am I a troubled kid? Yeah. You could say that."
• True Sight: Certain characters can see through the Mist. These are special cases, like Sally Jackson and Rachel Elizabeth Dare.
• Truth in Television: It's established in the series that Half-Bloods are commonly misdiagnosed with ADHD due to their over-active "battle reflexes", making them constantly on-guard and hyper-aware of their surroundings, and thus unable to concentrate on schoolwork. This is actually more-or-less the believed cause behind the development of ADHD; that it developed among hunter-gatherers during humanity's early days to aid in hunting and survival, and is only now noticeable because it's no longer useful for modern society.
• Tsundere:
  • Annabeth is initially mean to Percy, but whether this is due to him being a son of Poseidon or the fact they end up together is unknown.
  • Clarisse; while she's a bully, The Stolen Chariot side-story reveals her worst fear to be her father's anger.
• Trailers Always Spoil: If you see the cover of the first book and have any amount of Greek Mythology knowledge at all, you'll know that Percy is Poseidon's kid as soon as half-bloods are mentioned for the first time.
• Twisting the Prophecy: In The Sea of Monsters, before departing on her quest to find the Golden Fleece, Clarissa Le Rue receives a prophecy from the Oracle telling her she will "fail without friends, and fly home alone" seeming to spell her failure, leaving her terrified of disappointing her father Ares. Sure enough, despite making it to the island, it's Percy who captures the Fleece. However, Percy declares it still her victory as she brought them as friends, gives her the Fleece, and buys her a plane ticket so she can fly back to Camp Half-blood alone.

U

• Underside Ride: In The Sea of Monsters, Annabeth realizes that the sheep is Percy's way to sneak into Polyphemus' cave to rescue Grover and Clarisse. The scene cuts to Percy riding on the underside of Widget, one of Polyphemus's lighter-weight sheep, as an invisible Annabeth tells him to hang on.
• Underwater Kiss: Percy and Annabeth have one when they get together at the end of The Last Olympian.
• Underworld River: Styx, the river that separates the Underworld from the world of the living, is encountered and referenced multiple times. Its water will kill most beings that try to cross it, but those that can withstand it are made physically invulnerable except in one singular spot. Also mentioned are the Lethe, whose waters drain memory, and the Phlegethon, which runs with liquid fire. In The Heroes of Olympus, these rivers, alongside Acheron and Cocytus, are described as serving as something analogous to blood vessels for the world-body of Tartarus.
• Unperson: In The Titan's Curse, when it was discovered that Zoe Nightshade betrayed her sisters, the Hesperides, by helping Hercules, they kicked her out and any mentions of her were erased completely. It's implied, though, that she may have actually helped Hercules on all of his other nasty jobs, such as the Hydra and the Nemean Lion.
• Unreliable Narrator: Percy Jackson and the Greek Gods and Heroes are myths retold in-universe by Percy. As a result, there are snark-filled descriptions, various anachronisms in language and technology and in some cases, like the tale of Daedalus, events are incorrect compared to what we know really happened from the series proper.
• Unwitting Pawn: The gods, half-bloods, and practically everyone else throughout the series has been used as one at some point.
• Unusually Uninteresting Sight: Many demigod events that happen in public — they can have a fight with monsters and we will not notice anything.
  • The Laistrygonian fight in the start of The Sea of Monsters. Seriously, the coach must be deaf if he can't see that the new "visitors" are very dangerous (the Mist is implied to be responsible).
  • After The Titan's Curse, Percy and Annabeth both have matching streaks of grey in their hair from the effort of holding up the sky. This is never mentioned again, and none of the people who show up later notice this. The Heroes of Olympus establishes that they faded, so it's possible they're simply not there by the next book.
  • In The Last Olympian, the reason no one ever thinks Mrs. O'Leary is odd in Manhattan is because either they don't see her, or because (as Percy speculates) they actually see her as a truck of some kind.
    • A special mention goes to the "The Sword of Hades". While Percy was taking a test in the auditorium, Mrs. O'Leary, a hellhound the size of a Hummer, comes bounding in. Everybody else sees a poodle. Percy is understandably shocked by this.
• Uranus Is Showing: Averted because he is called Ouranos.

V

• Villain Has a Point: Luke, Prometheus, and most of the minor gods and demigods that side with the Titans do so because the Olympians are jerks, neglectful, and all around no better than the Titans. They side with Kronos either for revenge or because they hoped that by supporting him, he will grant them a better deal.
• Villain Forgot to Level Grind: The Minotaur was a major threat to Percy in Book 1, since he was untrained, unarmed, and had no idea he was a demigod. In Book 5, they meet again, but between his training with Annabeth and Luke, several life-or-death battles, wielding Riptide, and with the Curse of Achilles, Percy is now an absolute One-Man Army who beats the Minotaur in about five minutes.

W

• We Are as Mayflies: Humans, from the perspective of the gods or any of the other mythological races.
• We Can Rule Together: Luke offers this to Annabeth and Thalia.
• Weird Historical War: When discussing how demigods have impacted human history, Grover casually mentions World War II. Apparently it was fought largely between children of Zeus and Poseidon on one side and children of Hades on the other. Snatches picked up throughout the books suggest Hades' side was the Axis one.
• Weirdness Censor: The Mist, eventually revealed in The Demigod Diaries to be controlled by Hecate.
• Weirdness Magnet: Half-bloods have a scent that mythological creatures (mostly monsters) can pick out and follow. If you are not strong and/or are unaware that something's weird about you, the scent is weak enough to make monsters suspicious enough to check it out, but not enough to be certain. But if you realize you are not normal, the scent intensifies and can make monsters certain enough to attack; after that, you can basically count on monsters seeking you out in the real world and attacking every now and then. The reason demigods learn not to use cell phones is because cellular signals send messages to the monsters that say, "Here I am! Please rearrange my face!" At Camp Half-Blood, most of the camp activities involve combat, fitness, and survival skills for good reason.
  • The Demigod Diaries expands on this in the short story "The Son of Magic," wherein it's revealed that Lamia cursed all Half-Bloods to be easily detected by monsters in order to have revenge on Hera for cursing her.
• "Well Done, Son" Guy: This is one of the most primary themes in the series. Every half-blood yearns for their godly parent to respect, be proud of, or even just acknowledge them. But it's made clear that most of the gods simply don't really care or even remember a lot of their demigod children, which is why so many kids at Camp Half-Blood go unclaimed. This feeling of abandonment is precisely what caused Luke to side with Kronos, and convince so many other demigods to join him. The series ends with Luke's ultimate goal (to stop the gods from ignoring their children) being fulfilled, with it now being mandated that the Olympians must claim all their kids by the time they turn thirteen.)
• Whole-Plot Reference: Most books in the series have the general framework of one of the classics. Most notably is The Last Olympian, which parallels the Iliad in some places.
• Why We Can't Have Nice Things: Percy, in the case of Gabe's Chevrolet Camaro, Paul Blofis's Toyota Prius, Meriwether College Prep's gym, the St. Louis Arch, Alcatraz, Mount St. Helens, Goode Middle School's band room... New York City...
• What Measure Is a Non-Human?: Percy is much more willing to kill monsters than to kill humans. Justified because monsters come back to life eventually, just not in a very long time, fortunately.
  • He also can't kill regular people, at least with Riptide. As he learns when cornered by a street gang in Los Angeles.
• Wham Line: At least once per book.
  • From "The Battle of the Labyrinth":
    Percy: (to Quintus at Daedalus's workshop) What have you done with Daedalus?
    Quintus: My boy, you need lessons from your friend on seeing clearly. I am Daedalus.
  • In The Last Olympian, the line that foreshadows that Luke is not entirely gone inside Kronos is this both In-Universe and out.
    Luke/Kronos: You lied! You said they cared about me!
    Chiron: Me. You said me.
• Wicked Stepmother:
  • Subverted. Annabeth makes her stepmother out to be all sorts of resentful for bringing monsters around, but when we actually meet Mr. and Mrs. Chase in San Francisco... well, she turns out to be pretty nice.
  • Smelly Gabe is a male version, who was abusive to Percy. Paul Blofis is a male subversion — Percy expects him to be this but he's a straight-up Nice Guy.
  • The wives of the Big Three, as their husbands swore to never have demigod children after World War II. Hera and Persephone have very strained relationships with Thalia and Nico respectively. In contrast, while Amphitrite can act coldly towards Percy, she's not really the jealous type as she bakes him cookies and lets him leave his clothes on the floor.
• Wig, Dress, Accent: Silena Beauregard's Clarisse disguise in the last book. It fooled at least the important people. It is explained that this worked specifically because they wanted to believe it.
• World of Ham: It's a story about Classical Greek mythology, told in the style of a Classical Greek tragedy. This is almost a requirement.
• Writers Cannot Do Math: In book one, it's mentioned that Sally and Poseidon shared one summer together before he had to leave. Sally also got pregnant during this time period, as she was able to discuss the baby with Poseidon. But this becomes a problem when it's revealed that Percy's birthday is August 18th. This means Sally's entire pregnancy lasted three to four months, which (assuming human pregnancy with demigods works the same as a normal pregnancy) is far from the age of viability.

X

• Xanatos Gambit: In the Sea of Monsters, Luke reveals near the end that he planned to let the Olympians have the golden fleece in the end, anyway. When the fleece heals the tree, it also revives Thalia, daughter of Zeus, giving Kronos a second chance to convert a child of the Big Three to his cause. "It's just business, Jack."
• The X of Y: Title format used for a couple of books in the series:
  • The Sea of Monsters
  • The Battle of the Labyrinth

Y

• Ye Olde Butcherede Englishe: Zoe replaces all of her (second person) pronouns with this. Thalia gets extremely irritated with Zoe for this:
  Thalia Grace: For you. Not thee.
  Zoe Nightshade: But you use you for the beginning of a sentence.
  Thalia Grace: And the end. Not thou. Not thee. Just you.
  Zoe Nightshade: (throwing her hands up in the air) I hate this language! It changes too often!
• You Can See Me?: Percy is shocked when Rachel can see both his sword and the skeletons chasing him.
• You Can't Fight Fate: Not often, but there are a few instances.
  • It's lampshaded at one point. Annabeth tells the gods how trying to fight a prophecy almost never works (Yeah, Oedipus, ask your dad how that worked out), and the gods, who don't like being told ANYTHING very much, concede the point.
• You Know What You Did: Early in The Lightning Thief, Percy's attempts to ask the Furies why they are attacking him are met with this.
• You Monster!: Subverted.
  Annabeth: You're a monster.
  Geryon: What gave it away? Was it the three chests?
• Your Tomcat Is Pregnant: Inverted with the ophiotaurus, whom Percy starts calling "Bessie", a traditional name for a female cow, when he first meets it. Later, when the animal shows up after Percy got information from Nereus, Grover (who's meeting it for the first time) is able to translate its speech and identifies it as a male. Percy still refers to the animal as "Bessie" out of habit later, surprising even Poseidon.

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