"Good Morning", featured in this film and introduced in _Babes In Arms (1939)_, is a reworking of a 1920s Henderson-Brown composition, "This Is The Missus" (aka "Cash and Carry").
Gene Kelly insulted Debbie Reynolds for not being able to dance. Fred Astaire, who was hanging around the studio, found her crying under a piano and helped her with her dancing.
Debbie Reynolds had to rub her eyes with onions to make herself cry for the penultimate scene in the movie, when Kelly tells the audience that she, and not Lina, is the real star of "The Dancing Cavalier."
Debbie Reynolds remarked many years later that making this movie and surviving childbirth were the two hardest things she's ever had to do.
Cyd Charisse had to be taught how to smoke for her vampy dance sequence.
Judy Holliday had been the first choice to play silent-screen star Lina Lamont.
John Alton was initially hired as cinematographer after impressing Gene Kelly with his lensing of the ballet sequence in An American in Paris, but was fired over the objections of Kelly and Stanley Donen due to what Donen later described as "political reasons."
Howard Keel was the original choice to play Don Lockwood; however, he was replaced by Gene Kelly as the screenwriters evolved the character from a "Western actor" background to a "song-and-dance vaudeville" background.
Donald O'Connor admitted that he did not enjoy working with Gene Kelly, since Kelly was somewhat of a tyrant. O'Connor said that for the first several weeks he was terrified of making a mistake and being yelled at by Kelly.
Donald O'Connor smoked 4 packs of cigarettes a day throughout filming.
A microphone was hidden in Debbie Reynolds' blouse so her lines could be heard more clearly. During one of the dance numbers, her heartbeat can be heard, mirroring what happens to Lina Lamont in the movie itself.
After finishing filming the "Make 'em Laugh' dance sequence, Donald O'Connor found the effort so taxing that he went to bed for three days.
After they finished the "Good Morning" number, Debbie Reynolds had to be carried to her dressing room because she had burst some blood vessels in her feet. Despite her hard work on the "Good Morning" number, Gene Kelly decided that someone should dub her tap sounds, so he went into a dubbing room to dub the sound of her feet as well as his own.
Although uncredited, Gene Kelly had two incredibly talented choreography assistants. These ladies were none other than Carol Haney ("The Pajama Game") and Gwen Verdon (Broadway star of "Can-Can", "New Girl In Town", "Damn Yankees", "Redhead", "Sweet Charity" and "Chicago"). In fact, Kelly's taps during the "Singin' In The Rain" number were post-dubbed by Verdon and Haney. The ladies had to stand ankle-deep in a drum full of water to match the soggy on-screen action. Gene Kelly had also recommended Carol Haney for the role of Kathy Selden.
Before this film, dancer Cyd Charisse had only been in films as a 'dance specialty' or as a co-co star since 1944. Her torrid performance as the Louise Brooks-like vamp in the "Broadway Melody" fantasy number was so successful that it gave MGM the impetus to finally star her in pictures. Her next film was The Band Wagon, starring Fred Astaire.
Costume designer Walter Plunkett had worked in films since 1929, and some of his recollections were the source for gags about the perils of early sound shooting. Jean Hagen loudly "tapping" Gene Kelly with her fan in "The Dueling Cavalier" is based on a similar incident with Bebe Daniels and John Boles in Rio Rita.
Don and Cosmo were shown as touring through a variety of small towns as part of their vaudeville career. These included Dead Man's Fang (Arizona), Oatmeal (Nebraska) and Coyoteville (New Mexico). These are all fictional although there is a town called Oatmeal in Texas and one called Coyoteville in California.
Filming of the Cyd Charisse dance number had to be stopped for several hours after it was discovered that her pubic hair was visible through her costume. When the problem was finally fixed, the film's costume designer Walter Plunkett said, "It's OK, guys, we've finally got Cyd's crotch licked."
For the "Make Em Laugh" number, Gene Kelly asked Donald O'Connor to revive a trick he had done as a young dancer, running up a wall and completing a somersault. The number was so physically taxing that O'Connor, who smoked four packs of cigarettes a day at the time, went to bed (or may have been hospitalized, depending on the source) for a week after its completion, suffering from exhaustion and painful carpet burns. Unfortunately, an accident ruined all of the initial footage, so after a brief rest, O'Connor, ever the professional, agreed to do the difficult number all over again.
Freed's song, "Make 'Em Laugh" bore a striking similarity to Cole Porter's "Be a Clown" from the producer's 1948 film "The Pirate" although no one ever accused him of plagiarism.