The pimps' union is called the "Mec's' (tough guy's) Paris Protective Association" (MPPA), which also stands for "Motion Picture Producers Association", an organization which had given director Billy Wilder some trouble.
Charles Laughton was director-writer Billy Wilder's first choice to play the character of Moustache in Irma la Douce (1963) (1963). Laughton, who had given an Oscar-nominated lead performance under Wilder's direction in Witness for the Prosecution (1957), agreed to play the role, but died before principal photography commenced.
Shirley MacLaine signed on without having read the script because she "believed in Wilder and Lemmon".
Although the film was based on a musical, Billy Wilder did it as a straight comedy because he didn't feel comfortable staging singing and dancing numbers.
The sprawling $350,000 Rue Casanova set took three months to build and included 48 buildings and three converging streets.
Shirley MacLaine was not happy with the script, and thought even less of the film after it was finished, calling it "crude and clumsy". She was surprised to get a Best Actress Oscar nomination out of it, saying "I would have been nonplussed had I won it."
The original Broadway production of "Irma La Douce", the musical version, opened at the Plymouth Theater on September 29, 1960, ran for 524 performances and was nominated for the 1961 Tony Award for the Best Musical.
Had director Billy Wilder succeeded in getting the cast he wanted, Charles Laughton would have played barkeeper Moustache and Marilyn Monroe would have played streetwalker Irma. Years earlier Laughton and Monroe did appear on screen together in O. Henry's Full House (1952), with Monroe playing a streetwalker.
Throughout the film there are two small cars that go back and forth and are indeed the only two cars that appear in the film - one of the cars is a '53 Renault, the other seems to be a Peuguot.