Degrassi!
So, a few days ago, I compared one of the new Degrassi castmembers, Adam, to Lizzie from Life with Derek. Turns out, they're the same person. For reasons so far unknown, Adam is played by a girl, Jordan Todosey, who also played Lizzie. Oops! The ironic thing? In Vacation with Derek, the show's TV movie, Lizzie's love interest is played by another Degrassi cast member.