Many episodes are centered on a specific character. Most of them only appear in this special episode or perhaps in one or two more episode(s). Others have recurring occurrences or even are part of the main cast, but are especially in the foreground in a specific episode.
Some of the episodes centered on a specific character follow a specific formula. Among these are:
Freak of the week: The character of the week has super-powers, in most cases achieved by contact with kryptonite. He threatens, hurts or kills people and is overcome in the end, usually by Clark Kent. This type of single episode characters was especially frequent in the first seasons of the show.
Villain of the week: The character of the week is not a meteor freak, but a malevolent human or alien who may have or not have specific powers. He threatens, hurts or kills people and is overcome in the end.
Hero of the week: The character of the week is a benevolent character with some specific powers or super-powers who gets into trouble and is helped by Clark. He eventually joins Clark and helps him overcoming some threat.
Other episodes centered on a specific character do not fit in a specific formula. The charakters of the week in these episodes may be for example normal human beings without specific abilities, or benevolent metahumans or aliens.
A character of such an episode may already have appeared in minor roles in previous episodes, but have a prominent role in a specific episode. Even one of the main characters may become a character of the week, developing a special characteristic in an episode, such as Clark when coming into contact with red kryptonite.
Beside Harry Volk as the freak of the week, the episode also featured Cassandra Carver who had lost her vision in the meteor shower, but achieved the ability to see the future of people she touched. She died from the shock of the vision of Lex's future.
Beside Bob Rickman as the freak of the week, the episode also featured Kyle Tippet, Bob's former business partner who was with him during the meteor shower and got the same abilities, but had retired himself. In order to stop Bob's crimes, he used his abilities to make Bob shoot himself to death.
Ryan James, a boy who had the ability to read the minds of others, was used by his step-parents to commit robberies. He escaped them and went to live at the Kent Farm. He discovered Clark's secret, but promised not to tell anybody. He left Smallville with his aunt and reappeared in episode 2x08.
Beside Gary Watts as the villain of the week, the episode also focussed on Lana Lang who was caught by an explosion near Gary. Thereafter, she had visions seeing the abduction of Chloe with Gary's, the abductor's, eye, and was then herself abducted by Gary. She lost her ability to see with Gary's eye when he was shot to death by the police.
Clark bought a ring, not knowing that it contained red kryptonite which changed his character. He turned into a rebellious and dangerous teenager using his powers for personal gain instead of good. With the help of Pete, Jonathan succeeded in destroying the ring, whereupon Clark returned to normal.
The episode also featured Jessie Brooks, a new student on Smallville High School. Under the influence of the red kryptonite, Clark first flirted with her, but then stole CD's from her with data worth a million dollars. After Clark returned to normal, Jessie and her father left Smallville.
Ryan James from episode 1x16 was held captive in Summerholt Institute where his telepathic abilites were examined. He was freed by Clark, but soon knew he had an uncurable cerebral tumor. Before his death, he wanted to see the world from above, whereupon Clark gave him a ride on a hot-air balloon.
Pete and Chloe were infected by a parasitic worm from the Kawatche Caves which turned them into thrill-seeking daredevils. Pete used red kryptonite to get Clark to join them on a dangerous adventure. When the kryptonite fell out of his pocket, Clark saved Pete and Chloe as they drove their car off a cliff and brought them to the hospital.
Lucas Luthor, illegitimate son of Lionel Luthor and half-brother of Lex Luthor, had a criminal past in Edge City. When Lex found him and brought him home, Lionel and Lucas united to get Lex out of LuthorCorp. When Lucas learned that Lionel betrayed him, he united with Lex against Lionel. Lex regained his position in the company, and Lucas went away.
Virgil Swann, billionaire and scientist, had intercepted an extraterrestrial messsage and after years succeeded in deciphering it. He contacted Clark and told him about his real name Kal-El and his origin from the destroyed planet Krypton. He promised to keep Clark's secret and did so until his death in season 4.
Cyrus Krupp, a smallville high student, had achieved healing powers during the 1989 meteor shower. He had witnessed Clark's spaceship arriving, but believed himself to be the alien arrived by this chip. When healing a student who had bullied him at school and destroyed his space transmitter, Cyrus suffered a mental breakdown and was placed in a special hospital in Metropolis.
Clark Kent went to Metropolis committing robberies under the influence of red kryptonyte. He was restored to his normal self when the kryptonite ring was destroyed in his fight with Jonathan at the beginning of episode 2x02.
Lex Luthor was drugged so that he got hallucinations in order to make people believe he was schizophrenic. He was then taken to the Belle Reve Sanatorium from which he was released after an electroshock therapy to make him forget his last weeks in episode 3x09 .
Beside Joseph Altman as the villain of the week, the episode also featured Jordan Cross, a new Smallville High student who could foresee other people's death. He helped Clark seve Lana and the other girl and lost his ability in the explosion caused by Altman.
Beside Jason Dante as the villain of the week, the episode also focussed on Pete who was the champion at Dante's illegal street races. When Pete refused to intentionally throw a race, Dante tried to kill him by placing a bomb into his car. Pete, however, was saved by Clark.
Lex Luthor had himself treated in the Summerholt Institute to regain seven weeks lost from his memory by the electroshock therapy of episode 3x09. The Therapy let him remember scenes from his childhood.
Lindsey Harrison, a girl who had disappeared at the meteor shower, was taken into custody in the Kawatche caves by Jor-El and programmed to be the vessel of Clark's cousin Kara. She was disintegrated by Jor-El after she had brought Clark to him into the caves.
Clark Kent's and Lionel Luthor's spirits switched bodies when they both touched the Crystal of Water. Clark stayed in prison, but succeeded in getting Lionel there again and touching him with the stone so that they both switched back.
Lex Luthor was "split into two" after a kryptonite explosion with Lex as his good side and Alexander as his evil side. Alexander took Lex hostage. Clark came to free Lex, but Alexander subdued him with green Kryptonite. When Clark used his heat vision to turn the green kryptonite into black one, Alexander and Lex united again.
Evan Gallagher was found as a baby by Clark and Lana and taken to the Kent Farm. He aged in steps from a baby to a child and the next day to a boy of 16 years, each time setting free large amounts of energy. At the next step, he aged so far that he died, and Clark had to shield the energy which would otherwise have destroyed the surroundings.
Beside Buffy Sanders as the freak of the week, the episode also focussed on Lana Lang who was bitten by Buffy and also turned into a vampire. When Lana bit Clark, she acquired Clark's powers. In the end, Clark succeeded in injecting her an antidote into the heart whereupon she returned to normal and did not remember anything that happened.
Chloe and Lois investigated the dead of Melissa Paige. They found out she was a stripper in a club, and Lois started working in the club. She was abducted by Mr. Lyon, the murderer of Melissa Paige, who tried to fly her out of the country. Lois was saved by Clark, and Mr. Lyon was arrested at his return to Europe.
Clark was infected by a splinter of silver kryptonite. He got halluzinations that everybody was betraying him and begun to mistrust everybody, even Lana. When he attacked her, he was stopped by Milton Fine who claimed to be himself a Kryptonian and removed the splinter from Clark's body.
Lex Luthor was shot and fell into a coma. He had visions of his mother showing him how his future would be if he gave up power and money. He passed a Christmas with his wife Lana and their son. Im the end, however, Lana died because Lex could not afford the medical treatment she needed. Lex therefore decided not to renounce power and money.
Beside Tyler McKnight as the freak of the week, the episode also featured his daughter Maddie Van Horn who had the same ability to control glass as her father. After Clark had saved her from her father, she went to live at the Kent Farm and helped Clark to overcome her father. She finally went to live with her grandmother.
Lex Luthor was abducted by Milton Fine and prepared to be a vessel for Zod. He was endowed with the super powers of a Kryptonian. Jor-El ordered Clark to kill Lex with a kryptonian knife to prevent Zod from leaving the Phantom Zone. Clark threw the knife into Fine, instead, thereby opening a portal to the Zone, whereupon Zod took possession of Lex.
Oliver Queen used a drug called RL65 to heal wounds he had received during his missions as Green Arrow. The drug, however, had the side effect to make him more aggressive. When he and Lex shot each other, Clark saved Lex by injecting him the drug, too. Oliver then realized that the drug led him to kill people and stopped taking it.
Beside Jed McNally as the freakof the week, the episode also featured Javier Ramirez, a boy from Mexico who came to the USA with his friend Francisco in search of his mother. They were held as a slaves by McNally, but Javier succeeded in escaping. Clark helped him expose McNally and find his mother.
The episode also featured Daniel Kim, a shoe clerk at a bowling alley who had the power of telekinesis. He gave Lana bowling tips in an attempt to flirt with her and used his power to move Lana's ball to make it hit he pins. He was identified by Tobias Rice as a metahuman, abducted, and later killed.
Moira Sullivan, Chloe's mother, had the power to control other meteor infected people. Lex tried to use her to bring back a metahuman who had escaped from Level 33.1. When Chloe was brought to the place where her mother was held captive, they escaped with the help of Lowell and Clark. Soon after, Moira fell back into a catatonic state.
Jimmy Olsen was knocked unconscious after he took a picture of someone running away from a crime scene. He found himself in a black-and-white world of the 40es as a star reporter who got involved in a plot including Lana, Lex and Lionel as well as Clark as a detective. When he woke up, he remembered from his dream that a cigarette case was the clue to solve the crime.
Kara Kent searched for the blue crystal she got from her father. After breaking into a government lab, she was arrested by Agent Carter who subjected her to a memory treatment in order to learn her secret. Kara was rescued by Clark who then participated in Kara's memories of her past and learned about his mother Lara-El.
Lana Lang achieved Clarks powers when both were struck by a lightning in the presence of green kryptonite. She wanted to use her powers to take revenge on Lex. When she choked him, Clark intervened. In their fight, green kryptonite was set free. Clark then electrocuted Lana by which she lost her powers again.
Beside Zor-El as the villain of the weak, the episode also featured Lara-El, the mother of Clark, who also was re-created as a clone. She helped Clark to take down Zor-El and advised him to destroy the Blue crystal, whereby her clone was annihilated together with Zor-El's clone.
Pete Ross has got the ability of stretching his body by chewing some kryptonite-enhanced gum. He saved Kara from being slain by a piece of scaffolding falling down upon her. When he choked Lex, he was beaten up by one of Lex's men. He was saved by Clark, but had lost his powers.
Clark Kent was tranferred by Jor-El to an alternative reality in which he never had come to earth. His friends were doing fine, but Lex, who had become president of the United States, had been manipulated by Brainiac to start a nuclear war in order to destroy Earth. Clark then travelled back in time to Krypton to prevent Brainiac from killing baby Kal-El.
Oliver Queen was poisened and had only 12 more hours to live. In his agony, he remembered his time as a shipwrecked on an island where he was poisoned by a toxic plant and saved by Tess. Clark fetched an antidode from Brasilia and arrived just in time to save Oliver's life.
Lana Lang learned of Lex's Project Prometheus and wanted to have the Prometheus suit for herself. She underwent a painful medical treatment at the hands of Dr. Groll. In flashbacks, it is shown how Lana had been trained by Carter Bowfry to endure pain. Finally, the suit was fused with Lana's skin, giving her super powers.
Beside Davis Bloome as villain of the week, the episode also focussed on Jimmy Olsen who was in Metropolis General Hospital where he witnessed Davis killing a man. He searched Davis's ambulance car and found another corpse. When he accused Davis, he drugged him so that people believed Jimmy was hallucinating. Since also Chloe believed Davis, he left her, saying that their marriage was the biggest mistake in his life.
Davis Bloome was captured by Tess who had figured out that he had come to earth with Kal-El's ship as a boy. In flashbacks, Davis' past with the Luthors was revealed. Davis escaped and asked Chloe to help him die. In Dr. Groll's lab, Chloe emptied a tank of liquid green kryptonite on Davis so that he appearently died. He survived, however, because he was immortal.
Lois Lane posed herself as a vigilante called Stiletto and then pulished articles about this invented super-hero in order to come into contact with the Red-Blue Blur. When Clark, weakened by green kryptonite, was knocked down by Bruno Mannheim, Stiletto came to his rescue, but was herself saved by Clark from being shot by Bruno. Thereafter, she received her first phone call by the Red-Blue Blur.
Jor-El's clone from the orb arrived at the Kent Farm where Chloe told him about his son Kal-El. Zod abducted Jor-El because he believed that he had robbed him and his army of their powers, but kept them himself. When he learned that Jor-El had a son, he let him free in order to be led to the Blur. Clark found Jor-El with a mortal wound, and he died in his arms.
Brainiac had been reprogrammed by the Legion of Super-Heroes and was now a member of the Legion himself, called "Brainiac 5". He returned from the 31th century and took Clark with him on a journey through time to make him overcome his doubts about his past and his destiny and to show him that Lois would know his secret and always be with him.