The film was based on Murray Burnett and Joan Alison's unproduced play Everybody Comes to Rick's.[29] The Warner Bros. story analyst who read the play, Stephen Karnot, called it (approvingly) "sophisticated hokum"[30] and story editor Irene Diamond, who had discovered the script on a trip to New York in 1941, convinced Hal Wallis to buy the rights in January 1942 for $20,000 (equivalent to $320,000 in 2023),[31] the most anyone in Hollywood had ever paid for an unproduced play.[32] The project was renamed Casablanca, apparently in imitation of the 1938 hit Algiers.[33] Casablanca also shares many narrative and thematic similarities with Algiers (1938), which itself is a remake of the acclaimed 1937 French film Pépé le Moko, directed and co-written by Julien Duvivier.[34]
The original play was inspired by a trip to Europe made by Murray Burnett and his wife in 1938, during which they visited Vienna shortly after the Anschluss and were affected by the antisemitism they saw. In the south of France, they went to a nightclub that had a multinational clientele, among them many exiles and refugees, and the prototype of Sam.[35] In The Guardian, Paul Fairclough wrote that Cinema Vox in Tangier "was Africa's biggest when it opened in 1935, with 2,000 seats and a retractable roof. As Tangier was in Spanish territory, the theatre's wartime bar heaved with spies, refugees and underworld hoods, securing its place in cinematic history as the inspiration for Rick's Café in Casablanca."[36][37] The scene of the singing of "La Marseillaise" in the bar is attributed by the film scholar Julian Jackson as an adaptation of a similar scene from Jean Renoir's film La Grande Illusion five years prior.[38]
The first writers assigned to the script were twins Julius and Philip Epstein[39] who, against the wishes of Warner Bros., left at Frank Capra's request early in 1942 to work on the Why We Fight series in Washington, D.C.[40][41] While they were gone, the other credited writer, Howard Koch, was assigned; he produced thirty to forty pages.[41] When the Epstein brothers returned after about a month, they were reassigned to Casablanca and—contrary to what Koch claimed in two published books—his work was not used.[41] The Epstein brothers and Koch never worked in the same room at the same time during the writing of the script. In the final budget for the film, the Epsteins were paid $30,416, (equivalent to $442,473 in 2023) and Koch earned $4,200 (equivalent to $61,946 in 2023).[42]
In the play, the Ilsa character is an American named Lois Meredith; she does not meet Laszlo until after her relationship with Rick in Paris has ended. Rick is a lawyer. The play (set entirely in the café) ends with Rick sending Lois and Laszlo to the airport. To make Rick's motivation more believable, Wallis, Curtiz, and the screenwriters decided to set the film before the attack on Pearl Harbor.[43]
The possibility was discussed of Laszlo being killed in Casablanca, allowing Rick and Ilsa to leave together, but as Casey Robinson wrote to Wallis before filming began, the ending of the film
"set up for a swell twist when Rick sends her away on the plane with Laszlo. For now, in doing so, he is not just solving a love triangle. He is forcing the girl to live up to the idealism of her nature, forcing her to carry on with the work that in these days is far more important than the love of two little people."[44]
It was certainly impossible for Ilsa to leave Laszlo for Rick, as the Motion Picture Production Code forbade showing a woman leaving her husband for another man. The concern was not whether Ilsa would leave with Laszlo, but how this outcome would be engineered.[45] According to Julius Epstein, he and Philip were driving when they simultaneously came up with the idea for Renault to order the roundup of "the usual suspects", after which all the details needed for resolution of the story, including the farewell between Bergman and "a suddenly noble Bogart", were rapidly worked out.[46]
The uncredited Casey Robinson assisted with three weeks of rewrites, including contributing the series of meetings between Rick and Ilsa in the café.[47][48] Koch highlighted the political and melodramatic elements,[49][50] and Curtiz seems to have favored the romantic parts, insisting on retaining the Paris flashbacks.[51]
In a telegram to film editor Owen Marks on August 7, 1942, Wallis suggested two possible final lines of dialogue for Rick: "Louis, I might have known you'd mix your patriotism with a little larceny" or "Louis, I think this is the beginning of a beautiful friendship".[52] Two weeks later, Wallis settled on the latter, which Bogart was recalled to dub a month after shooting had finished.[51]
Bogart's line "Here's looking at you, kid", said four times, was not in the draft screenplays, but has been attributed to a comment he made to Bergman as she played poker with her English coach and hairdresser between takes.[53]
Despite the many writers, the film has what Ebert describes as a "wonderfully unified and consistent" script. Koch later claimed it was the tension between his own approach and Curtiz's that had accounted for this. "Surprisingly, these disparate approaches somehow meshed, and perhaps it was partly this tug of war between Curtiz and me that gave the film a certain balance."[54] Julius Epstein later noted the screenplay contained "more corn than in the states of Kansas and Iowa combined. But when corn works, there's nothing better".[55]
The film ran into some trouble with Joseph Breen of the Production Code Administration (the Hollywood self-censorship body), who opposed the suggestions that Captain Renault extorted sexual favors from visa applicants, and that Rick and Ilsa had slept together.[56][57] Extensive changes were made, with several lines of dialogue removed or altered. All direct references to sex were deleted; Renault's selling of visas for sex, and Rick and Ilsa's previous sexual relationship were implied elliptically rather than referenced explicitly.[58] Also, in the original script, when Sam plays "As Time Goes By", Rick exclaims, "What the —— are you playing?" This line was altered to "Sam, I thought I told you never to play ..." to conform to Breen's objection to an implied swear word.[59]
