- "Lana, I tell you you're beautiful because of who you are, not because of what I see. You're the girl I flew halfway around the world to be with, the girl who kicks my butt at Xbox and thinks it's hysterical. I mean, I've seen you with stomach flu; your eyes were all puffy and your nose was running... The reasons I tell you you're beautiful can't be seen in the mirror...that's good. I'm going to write that one down and use it later." – Jason Teague, to Lana Lang, Façade
On the eve of the eighteenth birthday of Lana, Jason took her to visit the tomb of Countess Margaret Isobel Thoreaux where she received the mystical Mark of Transference.
When Lana abruptly left Paris and returned to Smallville (to try to figure out what the mark meant), she did not explain why to Jason, so he followed her there. He enrolled in CKU and got a job at Smallville High School as the assistant football coach. Jason and Lana discreetly continued their relationship, and she eventually told him about the tattoo and explained why she returned. Jason vowed to be by her side as she searched for answers.
Jason had to start a working relationship with Clark when he requested to join the football team. Jason seemed to get on well with Clark, as he remained protective of Clark when the rest of the football team took a dislike to him. He also seemed to have faith in Clark to make a good impression with a Metropolis University scout.
Jason was forced to keep his relationship with Lana a secret, as he was en employee of her high school. He almost revealed it accidentally, after drinking the sports drink the cheerleaders had poisoned with kryptonite, but Lana was careful to avoid Jason in public. When he spotted Lana and Clark talking at practice, Jason instructed the football players to rough him up, despite Clark's obvious physical distress (due to drinking the kryptonite). He later attacked Clark in his barn, though he does not reveal to Clark which girl prompted his jealousy.
The effects of the drugged drink were cured before Jason could slip up in public, but it ultimately didn't matter. After Lex Luthor informed the school board that Jason was having a relationship with a student, he was fired anyway. Later, Lana began to notice changes in Jason's behavior when he began working with Lex, so she followed him to China. When they returned, she gave the Crystal of Air to Jason, but Jason began to suspect he was being manipulated by his mother. Jason realized that Genevieve orchestrated his and Lana's relationship from the beginning, and began to pull away from Lana. He broke up with her, saying he didn't think Lana was ready for a relationship, but eventually confessed the truth. Jason realized that, even if they didn't meet by chance, he still loved her and they got back together. Jason claimed that he was done searching for the Stones of Power, but continued to covertly help his mother recover them.
When Jason had a nightmare in which he catches Clark and Lana making out, then attacks Clark, he ends up falling from the balcony in the Talon and going into a coma. Lana becomes clearly upset and worried and stays with him at his bedside. It is later revealed to be a fear toxin that had infected Jason, which then infects Lana so that she sees everyone she loves die. After they were both cured of the toxin, Lana found Jason had a meeting for a LuthorCorp job offered to him by Lex, that he didn't tell her about. Jason said to Lana he was leaving Smallville since he didn't like what he was becoming. Lana sensed he is not telling her the full story, but Jason did not come clean as he was leaving.
When Jason broke up with Lana, she suspected that this was because he wanted a sexual relationship, Lana tried to seduce him in order to win him back. Jason admitted that this was not the reason that he ended the relationship and confided in her that he suspected his mother had orchestrated their meeting.
Jason along with Lana showed their contempt when Clark began dating Alicia Baker who had tried to kill Lana before. Lana was later showering when an unknown presence glided through the keyhole of her door of her apartment and tried to suffocate her with the shower curtain. Jason hear the commotion and broke into the bathroom just in time to save her.
At the hospital, Jason told Clark that Lana didn't want to see him. Lana and Jason were later at the Talon when Clark arrived to give his mom, Martha Kent, a ride home. Jason was reluctant to leave, even though he had homework but Clark and Martha convinced Jason that they would watch over Lana. As Jason was In his car about to leave, he was attacked from behind. A green scarf was pulled around his neck by the same unknown assailant. He managed to hit the car horn until Clark came out and saved him.
At the hospital, Lana had a run-in with Genevieve. Jason was reluctant to see her given his thoughts on how him and Lana met but Genevieve merely laughed away at Jason's theory that she orchestrated their "chance meeting." Jason became caught in the middle of Lex and Lionel Luthor, who were both earnestly seeking the Stones of Power. Lionel offered him a job at LuthorCorp to spy on Lex and his actions. Jason was given a copy of the map that Lex obtained, detailing location of the Crystal of Air.
Jason and Lex went to China, where they secretly searched for one of the mysterious Kryptonian crystals. However, they were arrested and interrogated by Chinese guards, and had to be saved by Clark Kent and Lana. Lana was possessed by Isobel, who obtained the Crystal of Air.
Jason and Lana are returning from a jog when they realize her Talon apartment has been broken into, but the only thing stolen is the Crystal of Air. Lana convinces Jason to forget about the stone, saying whoever took it can keep it. She tells him that she's tired of their relationship revolving around the Stones and Jason agrees to drop the subject. However, later, Jason goes to the Luthor Mansion and accuses Lionel Luthor of stealing the stone. He is in the process of roughhousing Lionel when Lana walks into the room.
Jason is hacking into Lex's email and finds a message that says he had a meeting with Ms. Crosby the same day her body was found. Lex catches him and Jason also asks him about an artifact mentioned in the email. When Lex won't answer his questions, Jason threatens to tell the authorities that a body was found but Lex seems unconcerned. Jason shows Sheriff Adams the spot where Crosby's body was found, but not only has the spot disappeared and been replaced by a gazebo, but Sheriff Adams announces that no database has a record that anybody by the name of Bridgette Crosby even existed. She is impatient with Jason's claims and Jason is frustrated that Lex has covered the whole thing up, but when she drives away, he makes a phone call to his mother and reports that everything went as planned—Lex took care of the body and he has the artifact from Bridgette.
Jason and Lana began to drift apart when Jason got upset when Lana announced that she was no longer going to enroll at CKU with him and that she's probably not going to college at all. She also stated that their relationship had changed outside of Paris. Angry, Jason yelled and claimed that he had done so much to protect her.
Genevieve continued to put pressure on Jason to locate the stones, and was dismayed that he actually did fall in love with Lana. When Lana stole the Crystal of Air, Genevieve tried to blackmail Lionel into giving it to her; Lionel, in turn, threatened her and Jason.
The Teagues then kidnapped Lex and Lionel, and held them hostage in a cabin. They forced Lex to try and get the location of the Crystal of Water. Lionel lied, saying that he sent it to Lana. Genevieve went to Lana's to find it, leaving Lex and Lionel under Jason's watch. They managed to get loose and tried to escape. Jason chased them into the woods, but Lex cornered him on a cliff over a river. Jason started to say something about Clark when Lionel appeared and shot him, and Jason fell off the cliff before he could reveal the secret information to Lex.
Jason somehow survived the fall and the shot and returned to Smallville the day of the second meteor shower. Having realized that Clark is somehow connected to the stones, he went to the Kent Farm and took Jonathan and Martha Kent hostage, threatening them with a shotgun to try and force the stones' location from them.
Jason was apparently killed when a meteor struck the Kent house directly above where he was standing.