The ad agency's viewing room has both color and black-and-white televisions side by side. This was common in the 1960s, allowing the executives to see how the commercial would appear in both color and B&W.
The pool used in the film was a part of the Universal theme park tour. (It would have been around 1968 or 1969.) The tram would go by the set with a car still in the water.
Producer Ross Hunter was furious when Walter Matthau asked for a salary of $100,000 (equivalent to about $875,000 in 2021). He cast (the less costly) Edward Andrews, instead.
Carl Reiner had intended the role of Beverly Boyer for Judy Holliday, but ill health prevented her from making the film. This was the first time that Doris Day stepped into a film role that had been intended for someone else. The next, Pousse-toi, chérie (1963), was originally being shot as Something's Got To Give (1962) starring Marilyn Monroe, whose firing from the movie led to that film's being recast and filmed with Day.
Two years after this film's release, Kym Karath (who plays the precocious five-year-old Maggie Boyer) won what is probably her best-known role, that of the youngest of the Von Trapp family singers in the box office behemoth La Mélodie du bonheur (1965).