Completely Different Title: In Soviet Union, the film was released as "V dzhaze tolko devushki," literally "In Jazz, There Are Only Girls," or poetically and figuratively "Only Girls Are Allowed In Jazz", thought by some to be a much more appropriate title.
Cut Song: Marilyn Monroe recorded a vocal version for the theme to the film. It was to be played over the opening credits, but an instrumental overture took its place in the final version. The title track later appeared on an LP in the mid-'70s, with Marilyn's three other songs from the film.
Deleted Scene: The lack of audience laughter during the first test screening prompted Billy Wilder to shorten the train ride from Chicago to Miami by 60 seconds. First, he trimmed the conversation Sugar and Josephine share in the bathroom: originally, Sugar told Josephine that she has trouble falling asleep in the berth above a snoring Beinstock, so she and Josephine agree to trade berths with each other. Next, he removed the payoff of this trade: Daphne mistakes a sleeping Josephine for Sugar, and grabs "her" while admitting that he's really a man. Joe/Josephine threatens to punch Jerry/Daphne, but the latter asks, "You wouldn't hit a girl, would you?" With the pacing increased, the movie met nonstop laughter at its next test screening.
Hide Your Pregnancy: Marilyn Monroe was pregnant during the filming, as a result she looked considerably heavier. Most of the publicity still photos were posed for by both Sandra Warner (who had an uncredited role as one of the band members) and Monroe's frequent stand-in Evelyn Moriarty with Monroe's head superimposed later.
Looping Lines: Tony Curtis' dialogue when he was dressed up as a female was dubbed by Paul Frees since Curtis had too deep of a voice to do a proper falsetto. He did attempt it during filming though, and one or two of his quick lines slipped through. Notably, Frees also had a small on-camera part as the owner of a speakeasy.
Marilyn Monroe sang a song to be played over the opening credits, but an instrumental version was used in the finished film.
According to some, the final line of the film was supposed to be "I know," but the censors wouldn't let it pass. The DVD bonus features instead say that Wilder and IAL Diamond wrote "Well, nobody's perfect!" as a "dummy line", intending to replace it with something funnier before the shoot, but they couldn't think of a worthy replacement.
Marilyn Monroe wanted the movie to be shot in color (her contract stipulated that all her films were to be in color), but Billy Wilder convinced her to let it be shot in black and white when costume tests revealed that the makeup that Tony Curtis and Jack Lemmon wore gave their faces a green tinge. Billy Wilder also thought black and white film gave the movie more of a Twenties atmosphere.
Jerry Lewis was offered the role of Jerry/Daphne but declined because he didn't want to dress in drag. When Lemmon received an Oscar nomination for the role that Lewis gave up, Lewis claims he sent him chocolates every year to thank him and now regrets not taking the part.
Bob Hope and Danny Kaye were considered for the lead roles, while Mitzi Gaynor was originally considered for the role of Sugar.
The role of Little Bonapart was originally offered to Edward G. Robinson, but he had vowed never again to work with George Raft, with whom he had a fist fight on the set of Manpower in 1941 when for a scene Raft spun him around too hard. (Despite the avowal, Robinson did co-star with Raft in A Bullet for Joey in 1955). However, the role of Johnny Paradise, the kid homaging Raft's "cheap trick" of coin-flipping, is also the man with the Tommy gun in the birthday cake who mows down Spats and his gang. The actor is Edward G. Robinson Jr.