Rick and Ilsa standing over Sam's piano in Paris was the first scene to be shot. Filming a tender love scene with two actors who had just met was not planned, but the filming of Now, Voyager had gone over schedule, so Paul Henreid and Claude Rains were not available.
Rick never says "Play it again, Sam." He says: "You played it for her, you can play it for me. Play it!". Ilsa says "Play it, Sam. Play 'As Time Goes By"'.
Rick's Cafe was one of the few original sets built for the film, the rest were all recycled from other Warner Brothers productions due to wartime restrictions on building supplies.
Several times the writers discussed having Rick leave with Lois/Ilsa, but this was always rejected (and the censors would not have allowed it with her married to Victor). Their major problem was to make it plausible that despite clearly loving Rick, she would leave with Victor; the final scene was rewritten many times until this was achieved.
Some years ago in a shop dealing with historic documents, a photo still from Casablanca was found, showing Rick sitting at the chess board. Accompanying the photo was a letter from Humphrey Bogart to a friend in New York, indicating a specific chess move. The document dealer explained that the chess game in the movie was a real game Bogart was playing by mail with his friend during the course of filming.
Studio publicity in 1941 claimed that Ronald Reagan and Ann Sheridan were scheduled to appear in this film, and Dennis Morgan is mentioned as the third lead. This was never the case, however, and the false story was planted, either by a studio publicist or a press agent for the three other actors, to keep their names in the press. Meanwhile George Raft was angling for the part with Jack L. Warner, but Hal B. Wallis had been assigned to search for what would be Humphrey Bogart's next starring role. He wrote to Warner that he had found the next movie for Bogart and the role was perfect for him. Nobody else was ever considered for the part.
The "Casablanca Hanger" at the Van Nuys Airport, built in 1928, was demolished in 2007.
The Allies invaded Casablanca in real life on 8 November 1942. As the film was not due for release until spring, studio executives suggested it be changed to incorporate the invasion. Warner Bros. chief Jack L. Warner objected, as he thought that an invasion was a subject worth a whole film, not just an epilogue, and that the main story of this film demanded a pre-invasion setting. Eventually he gave in, though, and producer Hal B. Wallis prepared to shoot an epilogue where Humphrey Bogart and Claude Rains hear about the invasion. However, before Rains could travel to the studio for this, David O. Selznick (whose studio owned Bergman's contract) previewed the film and urged Warner to release it unaltered and as fast as possible. Warner agreed and the premiered in New York on November 26. It did not play in Los Angeles until its general release the following January, and hence competed against 1943 films for the Oscars.
The difference in height between Humphrey Bogart and Ingrid Bergman changes throughout the film. This is because Bergman was actually a few inches taller than Bogart, though to create the illusion that it was vice versa, Michael Curtiz had Bogart stand on boxes and sit on pillows in some shots, or had Bergman slouch down (as evident when she sits on the couch in the "franc for your thoughts" scene).
The Epstein brothers finished their screenplay three days before the film began shooting; Howard Koch completed his two weeks after shooting had begun. All three were on call throughout the entire shooting period even though the Epsteins had been summoned to Washington to work on Frank Capra's "Why We Fight" documentary series.
The film cost approximately $950,000, some $100,000 over budget.
The film's success led to plans for a sequel, which was to be called Brazzaville. Ingrid Bergman was not available, so Geraldine Fitzgerald was considered for Ilsa before the project was killed. It was not until the late 1990s and Michael Walsh's novel "As Time Goes By" that a true sequel ever came to pass.
The first shot of Rick sees him playing chess, a personal favorite game of Humphrey Bogart's.
The first writers to tackle a screenplay were Æneas MacKenzie and Wally Kline, who spent six weeks on the project. Afterwards, Julius J. Epstein and Philip G. Epstein came on board, and their major contribution was the building up of Claude Rains' Capt. Renault character.
The French dialogue between Yvonne and the French officer translates as: French Officer: "Hey you, you're not French to go out with a German like that!" Yvonne: "What are you butting in for?" French Officer: "I am butting in..." Yvonne: "It's none of your business!"
The influx into Hollywood of large numbers of European exiles fleeing the war helped the casting enormously. In fact, of all the featured players in the film who get screen credit, only three were born in the United States: Humphrey Bogart, Dooley Wilson and Joy Page.
The last line is one of the most misquoted lines in all of film history. The correct line is, "Louie, I think this is the beginning of a beautiful friendship." It has been quoted as, "This could be the beginning of a beautiful friendship" or "I think this is the start of a beautiful friendship." This line was a last-minute addition, thought up by producer Hal B. Wallis and dubbed in by Humphrey Bogart after filming was completed.
The letters of transit that motivate so many characters in the film did not exist in Vichy-controlled France - they are purely a plot device invented by the screenwriters. Playwright Joan Alison always expected somebody to challenge her about the letters, but nobody ever did.
The movie's line "Here's looking at you, kid." was voted as the #1 of "The 100 Greatest Movie Lines" by Premiere in 2007.
The movie's line "Here's looking at you, kid" was voted as the #5 movie quote by the American Film Institute