Trivia

Farrah Fawcett was originally considered for the role of Julie Kotter, but ultimately producers felt audiences wouldn't believe she was Kaplan's wife. When Marcia Strassman got wind of this she was apparently very offended: "And you think I do look like Gabe Kaplan's wife? Thanks a lot!"

Groucho Marx was to make a cameo appearance in the episode "Sadie Hawkins Day". The planned scene was Kotter doing his frequent impression of Marx, then Marx appearing with his reaction. But when the 86-year-old Marx arrived on the set, it was decided that he was too weak to perform and the scene was scrapped. Marx posed for publicity photos with the cast but they were never released due to his frail appearance. Six years after Groucho Marx died, Gabe Kaplan would portray him in a stage play, filmed as Groucho (1983).

The original title of the series was to be simply "Kotter," but that was before composer John Sebastian had difficulty writing the theme song lyrics. He couldn't find enough rhyming words for the title. Giving up on that tack, he decided to compose lyrics that illustrated the premise of the show in a song called, "Welcome Back." The producers were so impressed with the song that they decided to change the series title to "Welcome Back, Kotter." The song was also released on a single which went to #1 on the charts.

In a 1978 People magazine article, Marcia Strassman stated that she did not get along with Gabe Kaplan and that she disliked working on the series. She tried to be released from her contract by publicly lambasting Kaplan. After Kaplan read the interview, he reached out to Strassman, and learned that producer James Komack was separately telling the two actors they didn't like each other, and Kaplan informed Strassman that he actually wanted more balance between Kotter's work and home environments, which would afford Strassman the chance to do more on the series.

Lawrence Hilton-Jacobs is the only cast member to appear in all 95 episodes of the series.