Billy Wilder came up with the idea for this film when he saw a player run into a cameraman on the sidelines while watching a football game.

Production was halted for weeks after Walter Matthau had a heart attack.
He had slimmed from 190 to 160 pounds by the time filming was completed, and had to wear a heavy black coat to conceal the weight loss.

Jack Lemmon originally had two other actors proposed to star with him, Frank Sinatra and Jackie Gleason, but he insisted that he do the picture with Walter Matthau.