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.
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.
The show was originally banned in Boston. The Boston ABC affiliate did not want to air the show at first because they thought it was about busing, a very heated topic at the time. They eventually ran the show with no problems.
The series was based on Gabe Kaplan's stand-up routine "Holes and Mello Rolls" in which he recounts his experience as a remedial high school student. The characters were based on his classmates named in the routine. Vinnie Barbarino was based on two classmates, Eddie Lecarri and Ray Barbarino. Freddie 'Boom Boom' Washington was based on Freddie "Furdy" Peyton. Juan Epstein was based on a classmate known as 'Epstein the Animal'. Arnold Horshack's name was unchanged. A line from the routine "Up your hole with a Mello Roll" became the show's catchphrase "Up your nose with a rubber hose".
Gabe Kaplan and John Travolta both left the show after the third season. Kaplan left after two episodes in the final season due to, creative differences with producer James Komack. Kaplan's name still in the credits but, he rarely appeared in the show. On the other hand, Travolta's original five year contract was altered after the massive success of Saturday Night Fever. Finally, Travolta appeared in eight of the 22 episodes, for $2,000 an episode and, he was billed as "Special Guest Star".
In the final season, the writing staff for the show was replaced by "seasoned comedy writers", who had earlier worked on Here's Lucy (1968), and other shows with actors much older than the high schoolers who were the focus of "Welcome Back Kotter". The new writers weren't capable of delivering the fresh, hip dialogue the show needed, and the ratings fell off quickly.
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. The rift split up the cast as Lawrence Hilton-Jacobs and Robert Hegyes sided with Kaplan and Ron Palillo sided with Strassman. John Travolta remained friendly with both. Palillo stated that he was happy when Kaplan left the series after the third season.
This sitcom was not aired in Italy until John Travolta's big smash on the silver screen as Tony Manero in Saturday Night Fever (1977), whose title was literally translated as "La febbre del sabato sera". This is why Italian adaptors decided to rename this sitcom "I ragazzi del sabato sera", i.e. "Saturday Night Guys".
During the opening and closing themes we see a sign that says "Welcome to Brooklyn: The 4th Largest City In America". The sign was located on the right shoulder of the eastbound Belt Parkway just after the entrance ramp from the Verrazano Narrows Bridge which connects Staten Island and Brooklyn. It was later modified and is now an overhead sign over the center lane in the same direction.
Ron Palillo explained later that his portrayal of Arnold Horshack was a blend of Dustin Hoffman's Ratzo Rizzo (from Midnight Cowboy (1969)), and a favorite aunt of Palillo's. His "Hello, my name is Arnold Horshack..." instantly won him the role.
The show was the US version of a very successful British sitcom called Please Sir, about an idealistic but slightly naive teacher, working at a tough London secondary school,called Fenn Street, teaching a class of occasionally rebellious and challenging 16 year olds. It ran on the ITV network from 1968 -72 and also included a feature film. A spin - off series called the Fenn Street Gang followed the teenagers after they had left the school.
"Ooo, Ooo I Do!" was supposed to air on May 25, 1979, but the episode was pre-empted when then-president Jimmy Carter gave a press conference about the recent fuel crisis in America. The episode was aired a week later and was intended as a series finale, but "The Breadwinners" aired after it.
Marcia Strassman (Julie Kotter) said she hated working on this show. She said her character was very boring and sumissive, and in particular she hated working with Gabe Kaplan who she said was very temperamental and difficult to work with. She expressed her displeasure to the press when she was on the show, saying she hopes it gets canceled. Ironically, now it's the main thing she's remembered for.
John Travolta incredibly appeared in 5 films during his tenure on Welcome Back Kotter: Carrie, The Boy in the Plastic Bubble, Moment By Moment, Grease and Saturday Night Fever. Grease was the highest grossing film of 1978, and during that year it was the third highest grossing film of all time!
Welcome Back Kotter was the inspiration and prototype for Facts of Life, which was basically supposed to be girls version of Kotter called Garrett's Girls with Charlotte Rae standing in for Gabe Kaplan as the lead, and Kim Fields, Mindy Cohn and Lisa Welchel the distaff Sweathogs. However, Facts of Life turned out to be much more successful than Kotter, lasting 9 seasons compared to Kotter's 4, becoming NBC's longest running sitcom up to that point, and still holding the record as the longest running show of any type with an all female cast
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 Gave Kaplan's wife? Thanks a lot!"