Playwright Philip Barry based the character of Tracy on Katharine Hepburn's public image at the time. She'd left her previous studio, RKO, on bad terms, which only worsened her (temporarily) unpopular image.
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.
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.
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 Broadway production of "The Philadelphia Story" by Philip Barry Jr. opened at the Shubert Theater on March 28, 1939, ran for 417 performances, closed on March 30, 1940 and starred Katharine Hepburn, Shirley Booth, Joseph Cotten and Hayden Rorke.
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 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.
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.