The Artifact: Once Stephanie left, his character moved into the background. By Degrassi High, he was Demoted to Extra. Ironically this would also happen to Ashley and her brother Toby in Degrassi: The Next Generation. Their characters were very much based on Steph and Arthur.
The Bus Came Back: He went to visit Spike for the last time in DH, the year after the accident who left him mentally disabled.
He seemed to be far higher-functioning in DH (when he was receiving intensive outpatient therapy while living at home with his family) than in TNG (after he had been warehoused in an institution his entire adult life).
Teen Pregnancy: Most of his plot deals with the problems he faces as a teenage dad. It ends after his drugged induced accident.
Badass: Though it's more a reputation than anything.
Chuck Cunningham Syndrome: Abruptly disappears after season two of DJH with only a passing mention by Caitlin in season three. He would be the first in a long line of Brother Chucks in the Degrassi franchise.
Actually he's the second, with Voula being the first.
Soap Box Sadie: Anti-abortion and pro animal rights. She is one of the few characters on television who is portrayed as pro-life, but not for religious reasons. She abhors abortion because her mother nearly aborted her.
Tsundere: To Joey early on, but after he tries to put the moves on her, goes to constant "tsun".
Chick Magnet: He has many girls crushing on him in both DJH and DH (Melanie, Spike, Michelle, Amy, Allison). Subverted in The Movie where, for some reason, he was unable to get any girl and even made fun of because of this.
Foreshadowing: In his very first appearance, running for student council against Stephanie, we see him standing on the steps of the school talking about what he'd change if he were in charge. Almost certainly nobody in 1987 knew what his being on the show would lead to, but the "..you won't recognize this school at all" scene at the end of The Boiling Point might be a deliberate Call Back.
Heroic BSOD: He is, unfortunately, the one to discover Claude's body in the bathroom. Though he bravely reports it, he is still very traumatized by it and drops out of school for a week or two to recover.
He Who Fights Monsters: "Hey Caitlin! I have a great idea for a date. Let's go spray paint slogans on a nuclear weapon parts making facility! And then I'll run away when I might get caught, leaving you out to dry!"
Break the Cutie: And how. He went from a fun loving and all around good guy (in the first 2 seasons of Degrassi Junior High) to a selfish, destructive jerk after his parents' death. And he only got worse in Degrassi High, to the point that even his best friends couldn't stand him anymore and his grandparents kicked him out of the house. Taken Up to Eleven in School's Out where other than a Jerk Ass he became also Drunk Driver and a murderer.
Ill Girl: Is diagnosed with Leukemia in season one of Degrassi High.
Put on a Bus: Her last appearance is during the first season of DH, and after that it's said that she's off adventuring with her dad after her brush with Leukemia. Lucy makes several video diaries for her, up until the very last episode of DH. However, none of this is present, nor is she in fact anywhere to be seen in School's Out.