Hit songwriter Jimmy Webb composed two songs for the soundtrack of this film, the title track, "How Sweet It Is," and "Montage," which appears at the midway point, when both Penny Marshall and Heather Menzies-Urich make their appearances below a portrait of the Mona Lisa. Both songs were performed by The Picardy Singers, neither became a hit.
In his autobiography, Terry-Thomas claimed he had been greatly irritated by co-star Debbie Reynolds, especially by her habit of telling him how to play comedy scenes. He said his reaction to her instructions was to listen attentively, thank her politely, and then go and do what he was going to do in the first place.
Although The Picardy Singers didn't have any hits out of the film, a band from Los Angeles, Love Generation, did score a minor success with their version of "Montage" (number 86 on the Billboard charts).
Director Jerry Paris and actress Ann Morgan Guilbert played husband and wife Jerry and Millie Halper in The Dick Van Dyke Show (1961).
Garry Marshall, a major baseball fan, likes to reference baseball in his work. In this instance, it's when Jerry Paris, as a brothel patron, wearing a baseball hat, glove, and holding a baseball while the working girl is wearing a catcher's mask, glove, and chest protector, yells out, "What inning is it?"