1. Mark-Paul Gosselaar (Zack) and Mario Lopez (Slater) were originally written and portrayed as bitter rivals for Kelly’s affections. However, Gosselaar and Lopez were (and still are) very close friends, so their on-screen relationship was changed to reflect the chemistry between to two actors.
2. Though Zack and Kelly were the big couple during the run of the series, Mark-Paul Gosselaar has admitted that he and Lark Voorhies (Lisa Turtle) were dating off-screen for most of the series’ run, with only one episode made where the two characters were a couple.
3. The Bayside High School set was never completely demolished after filming wrapped, and has since been reused in the shows “That’s So Raven” and “iCarly”.
4. Jennie Garth and Brian Austin Green from “Beverly Hills 90210″ both auditioned for the series and well as Jaleel White (Steve Urkle from “Family Matters”) and the late Jonathan Brandis.
5. Though they were portrayed as all the same age, Dustin Diamond (Screech) was 3 years younger than the rest of the cast.
6. Above the filing cabinet next to Mr. Belding’s desk is his degree in Kung Fu.
7. Mark-Paul Gosselaar had to dye his hair blond twice a week during filming.
8. There was only one classroom set that was constantly redressed as other classrooms.
9. Elizabeth Berkley originally auditioned for the role of Kelly Kapowski. When the part went to Tiffani Thiessen, producers created the role of Jessica Spano just for Berkley.
10. The Graduation finale had already been filmed when the network ordered more episodes. Elizabeth Berkley and Tiffani Thiessen were already committed to other projects, so a new character Tori (named after producer Aaron Spelling’s daughter Tori who also appeared in the series as Screech’s girlfriend) was introduced. Episodes with Tori were placed in the middle of the final episodes with no explanation for Kelly and Jessie’s absence, nor Tori’s absence when the Graduation episode was aired.