Columbia Pictures approached George Axelrod to produce a film version of his very popular play, "The Seven Year Itch," but the film rights were tied up as long as it was running on Broadway. He instead offered them "Phffft," an earlier play of his dealing with a similar subject.
The title "Phffft" comes from Walter Winchell's column, which was widely read during the 1950s. When a celebrity couple's marriage broke up, Winchell would describe the break-up as "phffft."
This was Jack Lemmon's second feature film and the second time he was paired on-screen opposite Judy Holliday. They were first cast together in It Should Happen to You (1954), Lemmon's debut film.
Late in the film, when Bob is assessing Nina's spending by check for her I.R.S. taxes, he mentions her spending includes a check written to Jean Louis. Jean Louis was the costume designer for the film, among many other Hollywood productions.
Jack Lemmon actually was a US Navy Ensign aboard the aircraft carrier USS Lake Champlain (CV-39) at the tail end of World War II.