Engel particularly envisioned one character, Zack Morris , who "would be that incorrigible kid who could lie to your face, letting you know very well that he's lying, and make you love him for it all the same. Engel's casting director, Shana Landsburg, finally happened across fourteen-year old Mark-Paul Gosselaar and was immediately struck by the teen's charisma, charm, and good looks. After a quick read-through, Gosselaar was immediately given the role. Gosselaar was asked to read through the script with a number of kids, and a second audition was scheduled for finalists.
It was Gosselaar himself who insisted that Dustin Diamond was right for the part as he believed Diamond was Screech in real life. After reading through the script, Diamond was given the part, although Engel later found out that he had misread his head shot and Diamond was considerably younger than the rest of the cast—a fact that, had he been aware, might have prevented Engel from casting him.
While still casting from the role, African-American actress Lark Voorhies was brought into Engel's office, and he immediately knew she was perfect for the role despite the fact that it meant rewriting the character.
Gerald Belding, as originally conceived on Good Morning, Miss Bliss, was an older, humorless man, and was played in the pilot by character actor Oliver Clark. Belding was rewritten to be significantly younger and to have a much different sense of humor  When Good Morning, Miss Bliss was retooled as Saved by the Bell, four actors and their respective characters from the original series were brought over to the new series: Gosselaar, Diamond, Voorhies, and Haskins.
The rest of the cast was fired, and Engel sought to replace them with new characters who would complement the old ones. Screech, Slater, Lisa, Mr.
Slater, was conceived as a young John Travolta type who would be an army brat and wear a leather jacket. He was originally conceived of as Italian-American.
However, when all efforts to cast the character were unsuccessful, Engel asked that the part be opened up to other races. Two days later, Mario Lopez , a dancer and drummer of Latino descent from Kids Incorporated auditioned for the role. Lopez was, by far, the best actor who auditioned, and was cast.
Engel had originally met Thiessen in while casting for Good Morning, Miss Bliss and was impressed with how much her acting had improved. He wanted her for the role, believing she had the perfect all-American girl appeal for the role, while others felt that Berkley, as the more experienced actress, would be a more reliable choice. Ultimately, Engel convinced the others after a read-through with Lopez, and Thiessen received the role.
Berkley originally auditioned for the role of Karen, a love-interest of Zack's on Good Morning, Miss Bliss, but lost the role because she was so much taller than Gosselaar at the time.
Engel believed that, now that her height was more even with the rest of the cast, she could be perfect. They were not having much luck in casting the third new character, Jessie Spano, who was conceived as a strong, feminist activist and a straight-A student, so Engel suggested offering the role to Berkley, who gladly accepted it. However, Thiessen and Berkley had already decided to leave the show. Though producers knew they couldn't replace Kelly and Jessie, they also knew they couldn't leave Lisa as the only girl on the show.
A new character, Tori Scott, was created as a cool but pretty biker girl who would also serve as a love interest for Zack and also act as a nemesis for him initially. Leanna Creel was cast for the part. Rather than develop a second new character, the producers decided to rely more on minor recurring characters such as Ginger, Ox, and Big Pete.
The series would focus on Miss Carrie Bliss, a recently married sixth grade teacher at the fictional John F. Kennedy Junior High School in Indianapolis. Though Sandy Duncan was originally considered for the titular role, the series ultimately became a vehicle for former British child star Hayley Mills.
Tartikoff didn't want to give up on the show, though, and made a deal with the Disney Channel to air thirteen episodes of the series in prime time. If the initial order did well, Disney was prepared to order an additional seven-seven.
Miss Bliss's class was changed from the sixth grade to the eighth grade, and the kids would be more central to the story. However, the show failed to pick up a following and did poorly in the ratings. By the time the last episode aired, Disney had already decided against ordering more. The elements featuring the kids had been well-received, so Tartikoff wanted to drop Miss Bliss from the show altogether and focus entirely on the teens.
NBC had been losing the high end of their animated audience, kids from ten to twelve, so the idea was to create a live action comedy to air on Saturday mornings, a new idea at the time. However, his wife convinced him that making the show would be a worthwhile endeavor, and he soon told Tartikoff he would do the show. In addition, they would film before a live studio audience. Though Engel hated the name, Tartikoff loved it.
The name stuck, and filming commenced, with the first episode, "Dancing to the Max," airing in prime time on August 20,