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.
This was director Billy Wilder's second film in a row in which one of his lead actors suffered a heart attack. In preceding film, 1964's Kiss Me, Stupid (1964), Peter Sellers' health problem forced Wilder to replace him with Ray Walston. In Fortune Cookie, Walter Matthau suffered attack midway through production but shooting was postponed until he recovered; his drastic weight loss from scene to scene is noticeable.
Walter Matthau had never worked with a director as precise as Billy Wilder, particularly when it came to the script. Although the director allowed the actors to rehearse as much as they wanted and to make suggestions, he insisted they stick closely to the script.
When Cliff Osmond asked Billy Wilder how to play the private detective, Wilder, always a man of few words where actors were concerned, said, "Incessant pursuit. Relentless. Play Javert [from Les Miserables]".
For later shots of the game, the Browns were playing elsewhere, so Billy Wilder substituted the Kent State football team. Spectators were lured to the stadium to serve as unpaid extras with the promise of free prizes, ranging from transistor radios to a new car. The latter was awarded to Wilder's wife, Audrey.
Lisa Linsky discovered the piano hidden in her folk's garage at the age of four. One of Lisa's fondest early memories is sharing a piano with fellow actor Jack Lemmon during the 1965-66 filming of the movie "The Fortune Cookie." (Lisa played the little girl on the skateboard in an early hospital scene.)
During a Cleveland Browns-Houston Oilers game at Cleveland Stadium on December 18, 1988, a cameraman, Mike Gallagher, was injured when Oilers wide receiver Haywood Jeffires and Browns defensive back Will Hill ran into him near the bleachers. The game was held up for 12 minutes.
The Browns' poor performance in the game prompted Cleveland fans to boo quarterback Frank Ryan. At a press conference afterwards, Billy Wilder stated, "...after my last picture, I know how [team owner Art] Modell feels. But he shouldn't worry. There'll be further disasters."