Monica Evans and Carole Shelley also reprise their roles in Disney's The AristoCats as a pair of English geese on a walking tour of France.
Billy Wilder was going to direct and write the screenplay at one point.
Walter Matthau, who played Oscar in both the original Broadway play and the movie, asked the play's author, Neil Simon, if he could play Felix instead. This was because Matthau thought Oscar's personality was too similar to his own and the role would be too easy; whereas playing the persnickety Felix would be a real acting challenge. Simon replied, "Walter, go and be an actor in somebody else's play. Please be Oscar in mine." Matthau finally agreed to it.
According to former Paramount production chief Robert Evans in his memoir "The Kid Stays in the Picture", producer Howard Koch originally wanted to use the Broadway cast, Walter Matthau (Oscar) and Art Carney (Felix) in the movie. Evans wanted Jack Lemmon for Felix. Evans also wanted Billy Wilder, who directed Lemmon and Matthau in The Fortune Cookie, as writer-director. The cost for the Lemmon-Matthau-Wilder package was $3 million plus 50% of the profits. Paramount owner Charlie Bluhdorn balked at the demands and personally took over negotiations. Wilder eventually dropped out. Lemmon was signed for $1 million against 10% of the gross and Matthau got a straight salary of $300,000.
At one point in the story (set in New York), Oscar says "Getting a clear picture on Channel 2" is not his idea of a fun evening. For years through the mid- to late 70s and early 80s, this movie was a staple of WCBS Channel 2's "Late Show" movie in New York City.
Despite the fact that a number of key scenes involve poker games, and the fact that the five male lead characters are all poker buddies, Felix is never seen actually playing poker.
During one scene, a sports radio program playing in the background reports an item about a baseball trade involving a player named Hank Moonjean. Hank Moonjean was actually the assistant director on this film.
The baseball sequence was filmed at Shea Stadium before a regularly scheduled contest between the New York Mets and Pittsburgh Pirates on June 27, 1967. Originally, Roberto Clemente was supposed to hit into the triple play. However, the fleet-footed Pirate kept beating the throw to first base. After several takes, Clemente slowed so much he appeared to be walking. Bill Mazeroski, a more lead-footed athlete, was offered the part instead.
The names of the English sisters, Cecily and Gwendolyn, are taken from Oscar Wilde's play "The Importance of Being Earnest".
The original Broadway production of "The Odd Couple" by Neil Simon opened at the Plymouth Theater on March 10, 1965, ran for 966 performances and was nominated for the 1965 Tony Award as Best Play. Walter Matthau won the 1965 Tony Award for Best Featured Actor.
The play starred Walter Matthau as Oscar, and Art Carney as Felix. When they were making it into a movie, they felt Carney didn't have enough box office punch, so they cast Jack Lemmon instead.
The two great friends, Jack Lemmon and Walter Matthau, are paired in a movie for the second of ten times.