"The Jewel of Techacal": Lex Luthor steals an allegedly cursed jewel from Lana Lang's uncle. When Superboy tries to stop him, he is weakened by the jewel's presence.
"A Kind of Princess": Clark Kent becomes attracted to Sara Danner, the daughter of a mob boss. Superboy must save her when she is kidnapped by the boss' enemies.
"Back to Oblivion": Mr. Wagner, who owns the scrapyard, starts reliving being in a concentration camp during World War II and kidnaps Lana thinking she is his granddaughter. Clark and TJ try to rescue her, but he sees them as Nazis and turns the scrapyard's machines against them.
"The Russian Exchange Student": A Russian exchange student named Natasha is blamed when Professor Gordon's demonstration for an improved version of gasoline is sabotaged. Clark and TJ realize she is being framed.
"Countdown to Nowhere": Criminals steal a laser weapon and plan to destroy a space shuttle.
"Bringing Down the House": When an amusement park's owner refuses to sell it to rock star Judd Faust, he starts to sabotage it with bombs. Lana starts dating him and is endangered as well.
"The Beast and Beauty": A Superboy imposter starts committing crimes in his name while trying to woo the beauty queen Jennifer Jenkins.
"The Fixer": Luthor bets on a basketball game and blackmails one side to lose. Superboy becomes the referee to stop this.
"The Alien Solution": A gaseous alien who can take over people's bodies aims to take over Superboy.
"Troubled Waters": A crooked businessman named Kenderson attempts to murder Pa Kent so that no one can oppose his scheme to buy all the farms in Smallville and get control of the water supply.
"The Invisible People": A crooked beach club owner named Gerald Manfred is willing to resort to kidnapping and murder to get rid of the homeless people on the beach.
"Kryptonite Kills": Kryptonite is discovered for the first time and Luthor learns how it can be used as a power source and to ward off Superboy.
"Revenge of the Alien: Part 1": The alien from "The Alien Solution" returns to seek revenge on Superboy.
"Revenge of the Alien: Part 2": The alien takes over Pa Kent's body and seemingly has Superboy where it wants him.
"Stand Up and Get Knocked Down": TJ investigates when his friend Michael dies. He finds Dexter, a crooked club owner, is forcing people to take lethal amounts of drugs.
"Meet Mr. Mxyzptlk": Mr. Mxyzptlk, an imp from the Fifth Dimension, causes havoc with his reality bending magic and attempts to woo Lana. Unable to fight him, Superboy learns he must trick him into saying his name backwards to get rid of him.
"Birdwoman of the Swamps": An old Native American woman uses magic to attack a construction crew attempting to work on her land. When Superboy helps them, she assumes he is evil and attacks him. Clark and TJ learn the crew's boss, Mr. Hogan, is crooked and must clear up the misunderstanding with the woman.
"Terror from the Blue": A bunch of dirty cops attempt to murder good cop Zeke Harris and Lana for witnessing them.
"War of the Species": Clark, Lana, and TJ visit a project for artificial intelligence but must deal with a killer android.
"Little Hercules": A boy genius named Billy Hercules hacks into a nuclear submarine's computer, but accidentally sets it to self-destruct. Superboy works with him to save the submarine.
"Mutant": Time traveling mutants from the 24th century kidnap a scientist and seek plutonium to make weapons.
"The Phantom of the Third Division": Ma Kent is kidnapped by Pa Kent's old Korean War comrade who blames him for getting captured and tortured and now wants Pa Kent to suffer like he had.
"Black Flamingo": Superboy investigates a nightclub where the owner is hypnotizing teens into becoming killers.
"Hollywood": Professor Zugar uses a time machine to send himself and Superboy to 1930's Hollywood. The time machine is damaged and while Zugar repairs it, Superboy protects the actress Victoria Letpur from stalkers.
"Succubus": A beautiful, vampire-like woman seeks to seduce TJ and Superboy.
"Luthor Unleashed": Superboy saves Luthor from a chemical explosion, but Luthor goes bald in the process. Now hating Superboy more than ever, Luthor sells a powerful weapon to assassins and tells them to kill him.
Season Two
"With This Ring, I Thee Kill": Luthor kidnaps Lana to force her to marry him and shoots Superboy with a special gun so powerful that he is paralyzed from the waist down.
"Lex Luthor: Sentenced to Die!": Professor Peterson tries to help Superboy recover from his paralysis and they try to figure out how to rescue Lana.
"Metallo": A mad scientist turns a criminal into Metallo, a cyborg with incredible strength and powered by kryptonite.
"Young Dracula": Bryon Shelly, a half-vampire, escapes his father and becomes a doctor, working on a serum to suppress his need for blood. An older vampire comes to take him home, with Superboy and Lana getting caught up in this.
"Nightmare Island": Clark, Lana, and Andy are stranded on an island when an alien takes away Clark's powers and kidnaps Lana.
"Bizarro... the Thing of Steel": Professor Peterson accidentally hits Superboy with a duplicating ray and creates Bizarro, a deformed duplicate with all his powers but limited intelligence. He causes a disruption and kryptonite has no effect on him.
"The Battle with Bizarro": Bizarro kidnaps Lana. He must be stopped soon because his body is unstable and may explode.
"Mr. and Mrs. Superboy": Mr. Mxyzptlk begs for help because a giant from the Fifth Dimension called Vlkabok is chasing him to get revenge for a prank. Mxyzptlk comes up with a zany scheme to get Vlkabok off his trail: Superboy and Lana must pretend to be married while he pretends to be their son.
"Programmed for Death": A robot takes on the personality of Andy's father and seeks to kill both Andy and his real father.
"Superboy’s Deadly Touch": Luthor zaps Superboy with a ray that causes him to lose control of his powers, especially his strength.
"The Power of Evil": An evil entity escapes a box, so its owner helps Superboy catch it.
"Superboy... Rest in Peace": A powerful android is sent from the future to kill Superboy. A woman is sent from the future to stop it.
"Super Menace!": A modified version of kryptonite turns Superboy evil. The military sends Metallo to stop him, but this backfires when they join forces instead.
"Yellow Peri's Spell of Doom": The demonic being Gazook turns the shy waitress Loretta York into the sorceress Yellow Peri. She tries to win Superboy's heart and attacks people he loves like Lana.
"Microboy": In an attempt to win over Lana, a student gains microwave-based superpowers and tries to become a superhero to outdo Superboy.
"Run, Dracula, Run": Byron Shelly is mugged and loses his serum. Losing control of himself, he bites Lana and turns her into a vampire, then they do the same to Superboy. The serum must be retrieved or else Lana and Superboy will be vampires forever.
"Brimstone": A magical doctor is chasing an evil spirit called Prodo. Prodo manages to curse Superboy and take control of him.
"Abandon Earth": What appears to be Superboy's Kryptonian parents, Jor-El and Lara, arrive and tell Superboy it is time to come home.
"Escape to Earth": Superboy finds out too late that his so-called parents were imposters and now he and his friends have been abducted. They must find a way to escape the aliens' ship.
"Superstar": Superboy protects a singer from killers.
"Nick Knack": A demented super genius called Nick Knack invents a suit that allows him to steal Superboy's powers.
"The Haunting of Andy McAlister": Andy, Superboy, and Lana are trapped in a pocket dimension simulating a Wild West town by the ghosts of outlaws who want revenge on Andy because his ancestor was the one who defeated them. To make matters worse, Superboy loses his powers.
"Revenge from the Deep": Lana becomes possessed by a spirit who wants revenge on an immortal man she once loved.
"Secrets of Superboy": Nick Knack kidnaps Andy and Lana and probes their memories to try to learn Superboy's secrets.
"Johnny Casanova and the Case of the Secret Serum": After Lana turns down a date with her tennis instructor, his mortally wounded brother comes with a potion he stole from the mafia. When he drinks it, he gains the power to charm people, which he starts using on both the mafia and Lana.
"The Woman Called Tiger Eye": A woman uses special crystals to control people's minds.
Season Three
"The Bride of Bizarro: Part 1": Bizarro returns and announces that he wants a mate. Luthor offers to make him one if he steals a supply of kryptonite.
"The Bride of Bizarro: Part 2": Luthor creates a Bizarro-Lana. Bizarro agrees to return the favor by killing Superboy.
"The Lair": Clark, Lana, and Matt investigate a man who was mutated by contaminated water.
"Neila": A superpowered alien woman named Neila challenges Superboy to a fight to see if he is worthy of being her husband.
"Roads Not Taken: Part 1": Luthor's girlfriend Darla asks Superboy to retrieve him from a portal. Superboy jumps through and finds himself in a world where his counterpart murdered his Luthor and became an outlaw.
"Roads Not Taken: Part 2": Superboy jumps through another portal and finds himself in a world where his counterpart is a dictator called The Sovereign and Luthor and Lana's counterparts are lovers and lead a resistance against him.
"The Sons of Icarus": The descendants of African slaves form a group called the Katia and gain the power to fly. Matt learns he is a descendant and is compelled to join them. Unfortunately, the Katia plan to burn the city to the ground.
"Carnival": A carnival owner steals the souls of his customers and wants to claim Superboy.
"Test of Time": Two aliens test Superboy's reactions after they accelerate him until it looks like time is frozen.
"Mindscape": An alien parasite attaches to Superboy and traps him in a series of nightmares while feeding on him.
"Superboy... Lost": Superboy loses his memories after deflecting a meteor that was heading for Earth. A mother and son who are hiding from the woman's abusive husband find and take him in.
"Special Effects": Monsters from a movie set are coming to life and attacking people.
"Neila and the Beast": Neila returns and asks for help because assassins and a Sasquatch-like creature are chasing her.
"The Golem": An elderly Jewish man creates a Golem to stop Neo Nazis, but when he dies, the Golem starts attacking anyone wearing a uniform, including police officers.
"A Day in the Double Life": Clark records his daily activities for his boss, of course covering up his activities as Superboy.
"Bodyswap": Luthor manages to switch bodies with Superboy.
"Rebirth: Part 1": When Superboy apparently causes a man's death, he retires in shame.
"Rebirth: Part 2": Lana believes Superboy was framed for the man's death and sets out to prove it.
"Werewolf": Clark and his friends help a woman who claims to have seen a werewolf.
"People vs. Metallo": Metallo is put on trial, but kryptonite is smuggled into the courtroom, allowing him to take it over and hold Superboy hostage.
"Jackson and Hyde": Jackson takes a potion that increases his strength and aggression. He is soon blamed for two murders, but there is actually someone else taking the potion.
"Mine Games": Superboy and Luthor are trapped in a caved in mine with kryptonite.
"Wish for Armageddon": Superboy finds he has unknowingly signed a contract with a demon that allows it to control him. Superboy must free himself before the demon uses him to destroy the world.
"Standoff": Clark and his friends are trapped when the building they are in is taken hostage. Clark must find a way to stop the criminals without revealing his secret identity.
"The Road to Hell: Part 1": Superboy is warped to a world where his counterpart is still a child and was raised in the jungle. He must stop the alternate Luthor from capturing and exploiting him.
"The Road to Hell: Part 2": Superboy is warped to another world that is a utopia, where its Luthor is a benevolent doctor and his counterpart is the adult Superman.
Season Four
"A Change of Heart: Part 1": When large screens playing positive messages are set up in the city, people start becoming violent. Lana starts dating Adam Verrell, the man behind the screens. Lana is found dead and Superboy is accused of her murder.
"A Change of Heart: Part 2": Adam faked Lana's death to frame Superboy and forces Tommy Puck, the screens' inventor, to improve them and make the people more violent.
"The Kryptonite Kid": Mike Walker's body is imbued with kryptonite after a lab explosion and becomes a superpowered criminal eager to destroy Superboy.
"The Basement": Lana finds an alien in a basement who takes on her form and tries to steal her identity.
"Darla Goes Ballistic": Darla drinks an experimental potion that increases her intelligence and grants her psychic powers. When she loses control of them, Superboy and Luthor must work together to cure her.
"Paranoia": When UFOs are spotted, government agents assemble, but when one is murdered, everyone is gripped by paranoia, accusing each other of being the murderer.
"Know Thine Enemy: Part 1": Luthor plans to wipe out humanity with nuclear bombs. To stop Superboy from interfering, he traps him in a virtual reality world where Superboy lives through Luthor's memories.
"Know Thine Enemy: Part 2": Lana rescues Superboy from the virtual world. As he attempts to stop Luthor, Lana tries to find Lena, Luthor's sister and the only person he truly loved, so she can talk him down from his plan.
"Hell Breaks Loose": The vengeful spirit of a clarinet player named Johnny who was murdered 50 years ago starts attacking people.
"Into the Mystery": While trying to reach his aunt Cassandra, who is dying of cancer, Clark repeatedly encounters a ghostly woman.
"To Be Human: Part 1": Bizarro-Lana randomly explodes, devastating Bizarro. He agrees to let Superboy and Dr. Lynn turn him into a normal human, but the process weakens Superboy. This allows an insane terrorist called Chaos to capture him.
"To Be Human: Part 2": Bizarro is now normal and calls himself Bill Zarro. When Chaos threatens to murder the weakened Superboy, Bill must choose whether to regain his powers and become Bizarro again, which is irreversible, to save Superboy.
"West of Alpha Centauri": Superboy and Lana are abducted by aliens and their jailers are all stronger than him. Their only hope of escape is get the bickering other prisoners to work together.
"Threesome: Part 1": Odessa Vexman, the prison psychiatrist, breaks Luthor and Metallo out of prison and they team up to finally defeat Superboy.
"Threesome: Part 2": While struggling to deal with this team-up, Superboy finds that a crooked casino is encroaching on Smallville.
"Out of Luck": A thief steals a rare coin that gives him good luck while cursing everyone else with bad luck, allowing him to evade Superboy.
"Who Is Superboy?": Lana goes to a supercomputer to try to find out Superboy's secret identity.
"Cat and Mouse": Clark is forced to see a psychiatrist to keep his job. When this includes a lie detector test, he is worried his secret identity might be outed.
"Obituary for a Superhero": When Superboy is caught in a kryptonite bomb explosion, his body cannot be found and everyone thinks he is dead.
"Metamorphosis": A gym owner is draining his patrons' youth to replenish his own. He believes draining Superboy will make him young forever.
"Rites of Passage: Part 1": When Superboy turns 21, his powers start to go out of control and the ship that brought him to Earth starts glowing. Dennis Jackson takes Lana and Matt to follow up on a 21 year old case involving a purple crystal.
"Rites of Passage: Part 2": The ship takes Clark's powers away and tells him he must retrieve the purple crystal and complete his rite of passage or else he will be powerless forever.
