The script for Casablanca was adapted by Julius and Philip Epstein and Howard Koch from an unproduced play called "Everybody Comes to Rick's" by Murray Burnett and Joan Alison.

No one knew right up until the filming of the last scene whether Ilsa would end up with Rick or Laszlo. During the course of the picture, when Ingrid Bergman asked director Michael Curtiz with which man her character was in love, she was told to "play it in between."

In Germany, one of the most famous, often quoted movie lines is "I look in your eyes, little one." This is the way German dubbers and subtitle writers chose to translate Casablanca's "Here's looking at you, kid."

Producer Hal B. Wallis considered Hedy Lamarr for the role of Ilsa, but she was then under contract to MGM. Lamarr later portrayed Ilsa in a 1944 radio show based on movie scripts, "Lux Radio Theater." At the time, both Bergman and Bogart were overseas entertaining the troops. Rick was played on radio by Alan Ladd.

"Rick's Café Américain" was modelled after Hotel El Minzah in Tangiers.

Conrad Veidt, who played Major Heinrich Strasser, was very well known for his hatred of the Nazis.

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"´.

Dooley Wilson (Sam) was a professional drummer who faked playing the piano. As the music was recorded at the same time as the film, the piano playing was actually a recording of a performance by Elliot Carpenter being played behind a curtain.

Producer Hal B. Wallis nearly made the character Sam a female. Hazel Scott, Lena Horne, and Ella Fitzgerald were tested for the role.

Humphrey Bogart's wife Mayo Methot continually accused him of having an affair with Ingrid Bergman, often confronting him in his dressing room before a shot. Bogart would come onto the set in a rage.

Wallis originally had Ronald Reagan and Ann Sheridan in mind for the lead roles. Pan Brennan, another producer, then said he thought Bogart Warner Brothers' most appealing star to women. Meanwhile George Raft was angling for the part with Jack L. Warner, but Wallis eventually chose Bogart.

Hedy Lamarr turned down the role of Ilsa, as she did not want to work with an unfinished script.

Paul Henreid was loaned to Warners for the role of Victor Lazlo by Selznick International pictures against his will. He was concerned that playing a secondary character would ruin his career as a leading romantic lead.

Bergman complained that she didn't know who her character was supposed to be in love with.

Two endings were scheduled to be filmed, but the first one worked so well that they used it.

The budget was so small they couldn't use a real plane in the back ground at the airport. Instead, it is a small cardboard cutout. To give the illusion that the plane was full-sized, they used midgets to portray the crew preparing the plane for take-off.

Director Michael Curtiz' Hungarian accent often caused confusion on the set. He asked a prop man for a "poodle" to appear in one scene. The prop man searched high and low for a poodle while the entire crew waited. He found one and presented it to Curtiz, who screamed "A poodle! A poodle of water!" See also Charge of the Light Brigade, The (1936).

This film was rewritten daily during filming, made on a shoestring budget, hastily released, and expected to bomb.

Many of the actors who played the Nazis were Jewish.

The timely real-life invasion of Casablanca was used to promote this film, and undoubtedly contributed to its success.

Many of the shadows were painted onto the set. [rumour]

Wallis thought of the film's last line 3 weeks after shooting ended, and Bogart was called back to dub it.

Captain Renault's line "You like war. I like women." was changed from "You enjoy war. I enjoy women." in order to meet decency standards.

Warners had intended to use "Horst Wessel," the main song of the Nazi party, during the "battle of the anthems" sequence, but the copyright was controlled by a German company, and Warners dropped that anthem for the lesser "Die Wacht Am Rhein" rather than violate the rights.

After shooting, Max Steiner spoke against using "As Time Goes By" as the song identifying Rick and Ilsa, saying he would rather compose an original song in order to qualify for royalties. But Hal B. Wallis replied that since filming had ended, Ingrid Bergman had cut her hair very short to film For Whom the Bell Tolls (1943) at a distant locale and therefore could not reshoot already-completed scenes that had used "As Time Goes By."

"As Time Goes By" was written by lifelong bachelor Herman Hupfeld and debuted in 1931's Broadway show "Everybody's Welcome", sung by Frances Williams. It had been a personal favorite of playwright and high school teacher Murray Burnett who, seven years later, visited Vienna just after the Nazis had entered. Later, after visiting a cafe in south France where a black pianist had entertained a mixed crowd of Nazis, French and refugees, Burnett was inspired to write the melodrama "Everybody Comes To Rick's," which was optioned for production by Martin Gabel and Carly Wharton, and later, Warners. Aftr the film's release, "As Time Goes By" stayed on radio's "Hit Parade" for 21 weeks. However, because of the coincidental musicians' union recording ban, the 1931 Rudy Vallee version became the smash hit. (It contains the rarely-sung introductory verse, not heard in the film.) Max Steiner, in a 1943 interview, admitted that the song "must have had something to attract so much attention."