Creator Peter Engel did not know Dustin Diamond's actual age (he was 12) when he cast Diamond as Screech, and later angered Diamond by repeatedly noting Diamond's immaturity relative to the other and older regular cast members. Engel also said that he would not have cast Diamond if he'd known he was 12 at the time.
Elizabeth Berkley originally auditioned for the role of Kelly Kapowski and was turned down in favor of Tiffani Thiessen, but the producers liked Elizabeth so much that they created the Jessie Spano character especially for her to play.
This show follows Good Morning, Miss Bliss (1987) which takes place at John F. Kennedy Junior High School, in Indianapolis, Indiana. When several of the students and Mr. Belding move up to Bayside High School in this series, it was suddenly set in Pacific Palisades, California.
The segments where Zach remembers his junior high school years were added to the beginning of Good Morning, Miss Bliss (1987) episodes that were re-edited from the Disney Channel as "Saved by the Bell" episodes for syndication.
The final "Graduation" episode had already been shot when the network ordered additional episodes. Tiffani Thiessen and Elizabeth Berkley were attached to other projects by that time, necessitating the creation of a replacement character Tori, played by Leanna Creel. The Tori episodes aired in the middle of the other final season episodes to sidestep continuity problems; the "Tori Paradox" was based on the idea that Tori, Kelly and Jessie were all at Bayside at the same time, and simply had different classes and different social interactions with Zach, Slater, Screech and Lisa that never overlapped.
Casper Van Dien made several uncredited appearances throughout the show's final year. He had one line in one show, and was often seen just as a simple background extra, mostly in the hallway scenes by the lockers.
According to producer Peter Engel, at a meeting before the show had been created, NBC President Brandon Tartikoff suggested the show be given a name that used the word bell (such as "When the Bell Rings"). One of Engel's colleagues then suggested the name "Saved by the Bell", which Tartikoff liked. Engel disliked the name but, believing that someone else probably owned the rights to the phrase "saved by the bell", went along with it. As luck would have it, NBC's legal department discovered that in fact nobody owned the rights to the phrase, and by the next day Engel's office was covered in large banners that said "Saved by the Bell".
Originally, Zack and Slater were written as bitter rivals for Kelly's romantic affections. Off screen however, Mario Lopez and Mark-Paul Gosselaar were (and continue to be) very close friends. The writers, sensing the obvious chemistry between the two actors, had the characters re-written as best friends, and they remained that way for the rest of the show.
The set of the school was never struck down completely after the show stopped production. It has been used and redressed on many shows that air on the Disney Channel and Nickelodeon since then, such as That's So Raven (2003) and iCarly (2007).
In the early 1990s, reruns of the show were being watched by an average of over 4 million viewers on the TBS cable station; this was equivalent to around 40 million viewers for programs airing in prime time on major networks.