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, from 1954.
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."
When Nina mentions she has her own TV show and is making $40,000 per year, that would equate to $354,000 in 2015.
Late in the film, when Jack Lemmon is assessing Judy Holliday'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.