Cocaine, Hookups & Cheating: 'Saved By The Bell' Cast's Secrets REVEALED In New Tell-All

Engel reveals that he was a "drug addict" before finding sobriety and religion in 1979. "Monday through Friday, I would wake up and smoke two joints, pop speed to get through work, snort a gram of cocaine, and take a handful of Quaaludes to fall asleep," he writes.

In 1987, the now sober Engel filmed a pilot that would later become Saved by the Bell, originally titled Good Morning, Miss Bliss. The first episode starred late child actor Jonathan Brandeis, Brian Austin Green, and Family Matters star Jaleel White.

Handsome SBTB star Mark-Paul Gosselaar hid a secret: he wasn't a true blonde! "His hair was naturally brown, just dyed blond for a movie on PBS," the producer reveals of the current Pitch actor.

Producers originally imagined A.C. Slater to look and act like a young John Travolta from Grease, but fell in love with Mario Lopez and changed the role to a Mexican American teen.

Beverly Hills, 90210 star Jennie Garth was a finalist to play Kelly Kapowski, a roll that ultimately went to Tiffani-Amber Thiessen.

Thiessen's acting skills were not as "developed" as her costars, but Engel was interested in her "visibility" as a teen model and future "icon."

Elizabeth Berkley's infamous episode about abusing caffeine pills was originally supposed to be about her problem with actual speed. But NBC's Standards and Practices thought hard drugs were "too serious."

Tori Spelling originally auditioned for a guest role as a favor for her famous producer father, Aaron Spelling. But Engel and the cast and crew ultimately liked her and hired her for multiple episodes.

Zack and Kelly forever! Gosselaar and Thiessen dated in real life, but only after their characters had split on the show.

As the show's father figure, Engel often had to lecture the misbehaving teens. "We had problems with cliques," he reveals. "There would be tears, flare-ups, accusations."

In 1991, Thiessen moved on to costar Lopez. "They made it very clear that they were now in a relationship — holding hands, being cutesy, etc," Engel claims.