Welcome Back, Kotter ended up being Travolta's breakout role, and he transitioned into movie stardom while he was still appearing in the show.
John Travolta became a fan favorite on Welcome Back, Kotter, but the iconic role almost didn't happen.
In the September issue of Emmy Magazine, Welcome Back, Kotter co-creator Gabe Kaplan opened up about the classic TV series, which ran from 1975 to 1979. The show, which celebrates its 50th anniversary this year, was based on Kaplan's stand-up comedy -- specifically his jokes about growing up in Brooklyn and attending a multicultural high school.
Eventually, Kaplan, now 80, and co-creator Alan Sacks decided that Kaplan should play a former student who returns to his high school as a teacher, who's now in charge of a remedial class of irascible teens. The group of young men became known as the Sweathogs.
Then they needed to cast the show. "[Casting director Lynn] Stalmaster thought a relative unknown named John Travolta would be perfect for Vinnie Barbarino," Kaplan wrote. Vinny is an Italian-American teen who's also the unofficial leader of the Sweathogs.
"But John had been offered a Broadway show, and rehearsals were starting soon," Kaplan wrote. Travolta had already been part of the cast of Grease on Broadway and in the touring company, though he played Doody instead of Danny Zuko. In 1974, he appeared in the Broadway musical Over Here!
Kotter turned out to be Travolta's breakthrough role. The show found massive ratings success in its early seasons and spawned merchandise like lunch boxes, dolls, trading cards and a board game. The theme song, "Welcome Back," written and recorded by John Sebastian, also became a No. 1 hit.
Kaplan remembered that early in the days of Kotter, he played a prank on Travolta, lying that he had lots of fan mail. The actor returned from the office disappointed. "But the next week? There was a canvas bag of about 500 letters. Big bag, no joke," Kaplan wrote.
Travolta also balanced movie roles with his TV stardom. He told PEOPLE in 1976, "I love slipping into the role of Barbarino. It's just that I have to do it so often." He said he was happy to keep going "as long as I have the freedom to do movies." In 1976, he starred in Carrie. Then, 1977 brought Saturday Night Fever and in 1978, Grease hit theaters, cementing his superstardom.
Welcome Back, Kotter was canceled in 1979 amid lower ratings. Travolta didn't return to television until he starred in 2016's The People v. O. J. Simpson: American Crime Story.
Kaplan wrote that he and Travolta didn't stay in close contact after the series ended. "His interview for this article was our first long talk in almost 50 years," he wrote. "But nothing had changed. We had a lot of fun."