Katharine Hepburn asked MGM to cast Clark Gable as Dexter and Spencer Tracy as Mike before she met either of them. Both Gable and Tracy were busy with other projects, so James Stewart was cast instead. MGM chief Louis B. Mayer allowed Hepburn a $150,000 salary towards casting the other male role, a sum that Cary Grant agreed to.
Playwright Philip Barry based the character of Tracy on Helen Hope Montgomery Scott, a Main Line Philadelphia socialite famous for throwing lavish parties at her family's 800 acre farm estate in Radnor. Filmmakers reportedly intended to shoot the film at Ardrossan (the name of the families estate), but decided against it after seeing the size and scale of the main house and the expansiveness of the estate. They reportedly thought that no one would believe that anyone could actually live like that, particularly in America in the 1940s.
The film was shot in eight weeks, and required no retakes. During the scene where James Stewart hiccups when drunk, you can see Cary Grant looking down and grinning. Since the hiccup wasn't scripted, Grant was on the verge of breaking out laughing and had to compose himself quickly. James Stewart thought of hiccuping in the drunk scene himself, without telling Cary Grant. When he began hiccuping, Grant turned to Stewart saying, "Excuse me." The scene required only one take.
Katharine Hepburn starred in the Broadway production of the play on which this film was based and owned the film rights to the material; they were purchased for her by billionaire Howard Hughes, then given to her as a gift.
James Stewart had no plans to attend the Oscar ceremony the year he was nominated for this film. Just before the ceremony began, he received a call at home "advising" him to slip into a dinner jacket and attend the ceremony. He did and he received the award for Best Actor. This was in the days before an accounting firm kept the Oscar voting results secret.
Before shooting the scene where Connor passionately recites his poetry to Tracy, James Stewart was extremely nervous and certain he would perform badly. Coincidently, Noel Coward was visiting the set on that day and, having been asked to say something to encourage Stewart by George Cukor, Coward off-handedly said something to Stewart like, "Did I mention I think you're a fantastic actor." Stewart shortly thereafter performed the scene without a hitch and went on to win the Oscar for Best Actor.
The original play was written specifically for Katharine Hepburn. Playwright Philip Barry wanted to woo the actress back to the stage after she had received disastrous reviews for the play "The Lake" on Broadway.
Some think, with director George Cukor on board, Katharine Hepburn's first choice of co-star, Clark Gable, was never going to be a possibility because Gable allegedly had Cukor fired from directing Gone with the Wind because Gable allegedly detested the director's obvious homosexuality. In reality, Cukor was dismissed from _Gone with the Wind (1939)_ because of repetitive clashes with producer David O. Selznick and Gable was simply busy with other projects at the time the The Philadelphia Story was being made.
James Stewart wasn't at all comfortable with some of the dialog, especially in the swimming pool scene, which also required him to act in a dressing gown. He said at the time that if he'd played the scene in just a swimming costume it would have been the end of his career.
The necklace that Dinah says "this stinks" about and later wears to entertain the reporters, is a copy of the necklace from Marie Antoinette's "The Affair of the Necklace". You can see it in Norma Shearer's Marie Antoinette, as well.
The original play featured a character named Sandy, who is Tracy's brother and the reason for Mike and Liz to come to the wedding. This character was deleted for the movie in order to beef up the character of Mike. There are several references in the film to a brother of Tracy's, but his name is Junius.
The word "Philadelphia" on the Oscar that James Stewart received in 1941 is misspelled. The Oscar was kept in the window of his father's hardware store located on Philadelphia Street in Indiana, Pennsylvania.