The car that Polly drives at the end is a 1958 Fiat 600, a most unusual car to be found in a small American town at the time.
On hearing of Peter Sellers' heart attack, Billy Wilder is reputed to have said, "Heart attack? You need a heart to have a heart attack!"
Production began with Peter Sellers in the role of Orville. Sellers suffered a heart attack several weeks into production, and filming was re-started with Ray Walston in the role (after Tony Randall, Bob Hope, Jack Lemmon,Danny Kaye and Tom Ewell were all considered).
The role of Polly the Pistol was originally written for Marilyn Monroe. However, her death in August of 1962 delayed the project. Jayne Mansfield was then considered, but had to withdraw due to pregnancy.
Crooner Dino is played by Dean Martin, in a role where he essentially is playing himself. Dino is asked at one point in the film what he thinks of the new rock group The Beatles, and he replies in a derogatory manner, with the script imitating Martin's feelings about the band in real life. Dino is then told that they are the new sound and that Dino's sound is obsolete. Ironically, and in reality, soon after the filming of this movie began, Martin recorded his soon-to-be signature song, "Everybody Loves Somebody Sometime," which knocked The Beatles' "A Hard Days' Night" single from the Billboard #1 spot in August 1964, one month after filming wrapped on this movie. Martin therefore became the second easy-listening performer to achieve a #1 Billboard single after The Beatles arrived in America. The first was Louis Armstrong with "Hello, Dolly" in May 1964. Both did this by usurping the Beatles themselves from the top chart position.