No adults appear on the series.
The entire first season only has seven different sets: the school hallway, the Avalon, Brooke's bedroom, Dylan's garage, the boys' locker room, the girls' locker room, and Billy and Courtney's apartment.
Chris William Martin (Dylan Blackwell), Todd Talbot (Matt Walker), Laura Harris (Ashley Frasier) and Ryan Reynolds (Billy Simpson) are the only actors to remain with the series throughout its entire run.
In Season 2, Laura Harris (Ashley Fraiser) was credited by her middle name, Elizabeth, as a first name. In Season 3, she was credited by her first name, Laura, and middle initial, E. In Seasons 1 and 4, she was credited by her first name only.
The season 2 show open contains several scenes that are not used in any of the episodes.