To create the effect of a vast sea of faces laboring grimly and impersonally at their desks in the huge insurance company office, designers Alexandre Trauner and Edward G. Boyle devised an interesting technique. Full-sized actors sat at the desks in the front and children dressed in suits were used at tiny desks toward the rear, followed by even smaller desks with cut-out figures operated by wires. It gave the effect of a much larger space than could have been achieved in the limited studio space.
Billy Wilder originally thought of the idea for the film after seeing Brief Encounter (1945) and wondering about the plight of a character unseen in that film -- the person who lends his apartment for an extramarital tryst. Shirley MacLaine was only given forty pages of the script because Wilder didn't want her to know how the story would turn out. She thought it was because the script wasn't finished.
For this film, Billy Wilder became the first person to win the Academy Awards for Best Picture, Best Director and Best Screenplay.
Jack Lemmon said he learned much about filmmaking from Billy Wilder, particularly the director's use of "hooks," bits of business the audience remembers long after they've forgotten other aspects of the movie. One such hook was the passing of the key to Baxter's apartment. Lemmon said for years after the picture's release, people would come up to him and say, "Hey, Jack, can I have the key?"
The office Christmas party scene was actually filmed on December 23, 1959, so as to catch everybody in the proper holiday mood. Billy Wilder filmed almost all of it on the first take, stating to an observer, "I wish it were always this easy. Today, I can just shout 'action' and stand back."
Billy Wilder: [Sheldrake] Wilder also used the character name Sheldrake in Sunset Boulevard (1950) and Kiss Me, Stupid (1964).