History Main / OnceASeason

* ''DoogieHowserMD'': Given that [[JustaKid Doogie’s young age]] is such an important factor in the series, his birthday (September 21) was always tied into the plot of every season premiere to pave the way into the next chapter of his life as a teenage doctor.

** It hasn't been explicitly stated as a deliberate tradition, but every year of New Who has had one episode when they go back in time and meet a famous British person and often use the story to fill in a mystery in said famous person's life:

*** Season 5: Winston Churchill

** It hasn't been explicitly stated as a deliberate tradition, but every year of New Who has had one episode when they go back in time and meet a famous British person who gets involved with the situation:
*** Season 1: Charles Dickens
*** Season 2: Queen Victoria
*** Season 3: William Shakespeare
*** Season 4: Agatha Christie

* ''PowerRangers'' has (not always, but typically) the arrival of the SixthRanger (even when it was one continuous story. S1: Tommy becomes Green. S2: Tommy, powers failing from mid S1 onward, loses them completely, sits a few eps out, returns as White. Zeo: Gold Ranger arrives. Doesn't stay. Turbo: Phantom Ranger arrives. Doesn't stay. Space: Silver Ranger awakens.)
** As well as the MidSeasonUpgrade and the ReunionShow.

* TheOC had the annual Christmukkah episode.

** Also each season had an [[BLAMEpisode "art episode"]].
*** Season 1 THE-FLY
*** Season 2 REPORT
*** Season 3 ARCHIVE
*** Season 4 FOODFITE
*** Season 5 none but season six made up for it with...
*** Season 6 HAMSTER and SCIENCE

* Each season of ''TeenTitans'' had one episode where things would go even zanier than normal. While most episodes had a somewhat serious plotline with a strong focus on characterization, these episodes would just toss all that aside and throw in as much surreal, nonsensical humor a they could.

* Apart from the Orange Islands or Johto, which didn't introduce one, the ''[[Anime/{{Ptitlei015gc004kw4}} Pokémon]]'' anime had Pikachu fry the bike of TokenGirl once per region.

** Let's not forget every Star Wars movie contained one BigNo per movie. Obi-Wan in I and II, Vader in III, and Luke in IV, V, and VI.

* ''StarTrekTheNextGeneration'' had yearly visits from Q (Apparently Gene Roddenberry wanted him to appear three or four times a season, but upon a lackluster second appearance they decided on a simple yearly visit). They also had the HolodeckMalfunction, which became a tradition for ''DeepSpaceNine'' and ''{{Voyager}}'' as well. Episodes about the [[TheWoobie painfully socially awkward and struggling]] man Lt. Barclay almost qualify after his introduction in Season 3, but didn't get one in Season 5 (instead getting two Season 6 episodes).

* ''StarTrekTheNextGeneration'' had yearly visits from Q (Apparently Gene Roddenberry wanted him to appear three or four times a season, but upon a lackluster second appearance they decided on a simple yearly visit). They also had the HolodeckMalfunction, which became a tradition for ''DeepSpaceNine'' and ''{{Voyager}}'' as well.

* ''StarTrekTheNextGeneration'' had yearly visits from Q (Apparently Gene Roddenberry wanted him to appear three or four times a season, but upon a lackluster second appearance they decided on a simple yearly visit). They also had the HolodeckMalfunction, which became a tradition for ''DeepSpaceNine'' and ''{{Voyager}}'' as well.
** ''DeepSpaceNine's'' producers allowed Colm "O'Brien" Meaney time off regularly to maintain his film career, so when they did have full access to him, they regularly put his character through the mill, either by having him serve thirty years for murder (albeit AllJustADream) or have his daughter disappear into a time rift or whatever. The "torturing O'Brien" episode became a tradition.
* ''BuffyTheVampireSlayer'' had "Buffy's Birthday" episodes, where something always crashed her party. In the third season it seemed like Spike and Ethan Rayne were going to make yearly visits, but Spike [[PromotionToOpeningTitles became a cast member]] and Ethan wasn't seen after Season 4.
** Spike [[LampshadeHanging lampshades]] how something terrible happens on Buffy's birthday in the season six episode.
** Oh, yeah, and every season has a [[TheWorldIsAlwaysDoomed minimum of one attempt to destroy the world]]. This would often be the SeasonFinale, but sometimes it would come in the middle of the season, in which case it was rarely taken that seriously.
** The producers also commented that they worked hard to give Giles one line per season that sounds absolutely crazy out of context, and to lampshade its craziness. Their personal favorite was from Season 3's episode "Gingerbread":
--->'''Giles''': We need to save Buffy from Hansel and Gretel!
--->'''Cordelia''': Now, let's be clear, the brain damage happened before I hit you.
* ''{{House}}'' would often towards the end the season (if not the SeasonFinale) have some sort of hallucination episode, sort of started by the "Three Stories" episode in the first season that had House using hypothetical situations to better understand a few medical dilemmas.
** House would also have one antagonist per season. Vogler, Tritter and Amber all play this role, as does Stacey's husband. [[spoiler:Amber occupies the position for two series in a row, in fact]].
* In the webcomic ''{{Ozy And Millie}}'', there is a story arc that occurs once a year in which Ozy somehow loses all his fur. This is explained to be because of a family curse that only effects Ozy because he's the only member in the family to actually have fur. It is later explained that the whole curse story was a lie told to him by his father. ItMakesSenseInContext.

* Several recurring jokes on ''{{Peanuts}}'' occured once a year. These included Lucy pulling away the football when Charlie Brown tries to kick it, Linus awaiting the Great Pumpkin, and Schroder celebrating Beethoven's birthday. There were also strips commemorating D-Day, and Snoopy going to drink root beers with Bill Maudlin every Memorial Day (based on Charles Schultz's real-life ritual with Maudlin, a cartoonist famous for his satirical cartoons on military life during WWII).
* The newspaper comic ''{{Curtis}}'' is renowned for its bizarre and [[BigLippedAlligatorMoment over-the-top]] Kwanzaa stories, which are often the most entertaining comics he does.
* ''TheSimpsons'' and their annual Treehouse of Horror episodes.
** Sideshow Bob comes to commit some crime
* Apart from the Orange Islands or Johto, which didn't introduce one, the ''[[Anime/{{Ptitlei015gc004kw4}} Pokémon]]'' anime had Pikachu fry the bike of TokenGirl once per region.
** Ash and crossdressing also goes OnceASeason.
* ''PowerRangers'' has (not always, but typically) the arrival of the SixthRanger (even when it was one continuous story. S1: Tommy becomes Green. S2: Tommy, powers failing from mid S1 onward, loses them completely, sits a few eps out, returns as White. Zeo: Gold Ranger arrives. Doesn't stay. Turbo: Phantom Ranger arrives. Doesn't stay. Space: Silver Ranger awakens.)
** As well as the MidSeasonUpgrade and the ReunionShow.
*** The crossover specials didn't always happen (Ninja Storm and RPM, but that was likely for other reasons). ''SuperSentai'' always had a crossover movie though.
* ''[[TwentyFour 24]]'': Around episode eight, the Big Nasty Thing That's Going On turns out to be a small portion of the BigBad's overarching plan.
** And around episode 14, that BigBad is stopped and revealed in a side plot to be actually either TheDragon of the BiggerBad / EvilOverlord, or a free or ancillary agent whose operation was actually ''damaging'' the EvilOverlord's one.
** On a more ''meta'' level, since as early as Season 1, ''24'' has managed to predict an important item (usually a failure) of US foreign politics or military operations that actually takes place next year or a couple of years later '''in real life''': the first African-American President in Season 1 (way before its time); the US government [[AcceptableTargets blaming terrorist attacks on Middle-East countries]] to start a war for oil in Season 2; tortured or neglected agents defecting to the other side in Season 3; excessive demonization of arabs in the public media in Season 4; the US getting involved in the (mis)relationship between "mother Russia" and her annexed territories Season 5 (not to count revealing the President as the evil behind actually trying to start a war). Seasons 7 and 8 being the most recent ones it is not clear yet what ''24'' is going to end having predicted but it may be related to Sarah Palin as the first female President or American firms testing bioweapons in African countries (S7), or [[spoiler:the permanent damage that former Presidents have over the Office]] (S8).
** Ever since Season 2, [[AnyoneCanDie someone important]] dies at 02:00 AM, or during the episode running that hour:
*** Season 1: former CTU District Manager [[TakeUpMySword Richard Walsh hands evidence to Jack and dies]] right before the hour (setting part of the tone of the series).
*** Season 2: Jonathan Wallace (the villain who carried the Cyprus Audio). Also, Jack "dies" at the end of the hour.
*** Season 3: Nina Myers dies at the end of the hour, [[ItsPersonal at the hands of Jack]].
*** Season 4: both [[DeathOfTheHypotenuse Paul Raines]] and a witness brought by Jack from the Chinese consulate.
*** Season 5: the [[InvertedTrope inversion]]: former Secretary of Defense James Heller is confirmed to have ''survived'' an attack that took place near the end of the previous hour.
*** Season 6: Milo Pressman, feigning being the director of CTU to protect its personnel from a raid, dies during the hour.
*** Season 7: [[HeelFaceRevolvingDoor Tony Almeida]] killed Larry Moss shortly before the hour, and kills his own accomplice at the end of the hour.
*** Season 8: a kid sent by the terrorists to kill a loose end is remotely detonated near the end of the hour. Also, the villain who appeared to mastermind the events up to that point, and who the terrorists were trying to kill, is confirmed to have been ''already'' dead during the hour (part of Jack's ploy to draw the terrorists to the open).

* For a movie format, ''StarWars'' did this purposefully.
** ThePhantomMenace / ANewHope: Young kid pilot managing a lucky shot to destroy a massive battleship.
** AttackOfTheClones / TheEmpireStrikesBack: A battle in an asteroid field zig-zagging around massive chunks of rock.
** RevengeOfTheSith / ReturnOfTheJedi: A duel between an apprentice and someone being manipulated into becoming the next apprentice.
* ''{{Cheers}}'' had the yearly "Bar Wars" episodes, in which Cheers and another local bar (Gary's Old Towne Tavern) competed to top each other in practical jokes.
* Each season of ''TeenTitans'' had one episode where things would go even zanier than normal. While most episodes had a somewhat serious plotline with a strong focus on characterization, these episodes would just toss all that aside and throw in as much surreal, nonsensical humor a they could.
* ''{{Garfield}}'' always had birthday strips, mostly about how much Garfield dreads them.
* ''LegendOfTheSeeker'' seems to be following the example of [[SwordOfTruth the novel series it's based on]], with a new Wizard's Rule each season.

* Several of the characters on ''{{Frasier}}'' make seasonal guest appearances, including his agent Bebe, his ex-wife Lilith, and their son Frederick.
** Like holiday episodes, the Seabees (Seattle Broadcast Awards) by definition came up only once a year.
* ''{{NCIS}}'': Tony gets framed for a homicide OnceASeason. He is GenreSavvy enough to notice and lampshade it, but [[WrongGenreSavvy not enough to prevent it]].
** Gibbs builds and (somehow) disposes of a boat in his basement once a season.
* In every season finale of ''{{Charmed}}'', the last shot is the front door of the Halliwell Manor closing, either being magically closed by Prue (seasons 1 and 2), another supernatural being (seasons 3 and 4), Chris (season 5), itself (season 7) or [[spoiler:Piper's granddaughter]] (season 8). The only exception is season 6, the final shot shows the doors of a hospital room closing.
** Though in the season 6 finale, Chris does magically close the front door. Only this time it happens during the episode (when he throws Darryl out) , and not at the very end.

* ''StargateSG1'' has {{Clip Show}}s. Not quite every single season, but it seemed that way for a while.
* ''PrettyCure'', for its first five seasons, had a number of traditions: infighting in episode 8, new mascot introduced just before the midseason powerup, new mascot runs away from home shortly after, just to name a few. Most of these were done away with along with the ArtShift and the name-based mascot [[VerbalTic sentence enders]] come ''FreshPrettyCure''.

* ''{{Slayers}}'' had one [[WholesomeCrossdresser Cross Dressing]] episode every season, and it was always episode 17.

* Apart from the Orange Islands, which didn't introduce one, the ''[[Anime/{{Pokemon}} Pokémon]]'' [[Anime/{{Pokemon}} anime]] had Pikachu fry the bike of TokenGirl once per region.

** House would also have one antagonist per season. Vogler, Tritter and Amber all play this role, as does Stacey's husband. [[Spoiler:Amber occupies the position for two series in a row, in fact]].

** House would also have one antagonist per season. Vogler, Tritter and Amber all play this role, as does Stacey's husband. [[Spoiler: Amber occupies the position for two series in a row, in fact]].

* ''{{Cheers}}'' had the yearly "Bar Wars" episodes, in which Cheers and another local bar (Gary's Old Time Tavern) competed to top each other in practical jokes.

** Sideshow Bob comes to committ some crime