The pie fight scene lasts four minutes and was shot in five days. It is the longest pie fight sequence in movie history. At first, the cast had fun filming the pie fight scene, but eventually the process grew wearisome and dangerous. Natalie Wood choked briefly on a pie which hit her open mouth. Jack Lemmon got knocked out a few times: "a pie hitting you in the face feels like a ton of cement". At the end of shooting the fight, when Blake Edwards called "Cut!" he was barraged with several hundred pies that members of the cast had hidden, waiting for that moment.
This film was the inspiration for the Saturday morning cartoon show Wacky Races (1968): Dick Dastardly and his sidekick Muttley were based on Professor Fate and Max, Penelope Pitstop was based on Maggie DuBois and Peter Perfect was based on Leslie.
Jack L. Warner asked Tony Curtis if he would give a percentage of his film royalties to Natalie Wood as an inducement, but Curtis refused. He said, "I couldn't give her anything to make her want to do the movie." In the two films Wood and Curtis worked on previously, they developed an acrimonious relationship.
Chris Lemmon, son of actor Jack Lemmon (Professor Fate), said in an interview on KMOX-Radio in St. Louis that he considers Lemmon's role in this film to be his father's finest. Jack Lemmon himself has said he got more mail about Fate than about any other character he played.
In the film's press kit, Natalie Wood divulges that she took fencing lessons, sidesaddle lessons and practiced smoking cigars, but her biggest challenge was driving the Stanley Steamer. The steering was difficult ("like turning a tractor, I suspect", she says) and going into reverse was nearly impossible.