Gene Kelly directed the whole "Embraceable You" sequence.
Vincente Minnelli first wanted Maurice Chevalier in the Georges Guétary part, and Celeste Holm in the Nina Foch part. But Chevalier wasn't available; Minnelli was pleased with Foch's reading, and she got the part.
Leslie Caron had suffered from malnutrition during WWII and was not used to the rigorous schedule of filming a movie. Because she would tire so easily, she was only able to work every other day.
Cyd Charisse discovered that she was pregnant during pre-production and was replaced by Leslie Caron.
Arthur Freed originally just wanted to buy the rights to the George Gershwin number "American in Paris," but Ira Gershwin made the condition that he'd only sell on the condition that if a musical were to use the song, it would use only Gershwin numbers as its other songs.
Oscar Levant and Gene Kelly both grew up in Pittsburgh. Kelly appeared in a Cap and Gown show at the University of Pittsburgh whose music was written by Oscar's talented musical brother, Benjamin, who went on to become a urologist.
Oscar Levant, more of a pianist than an actor, signed onto the film because he was actually a friend of George Gershwin.
Oscar Levant's dream sequence may be a tribute to Buster Keaton. In the opening sequence of The Play House, Keaton also played every role - conductor, every member of the orchestra, stage hand, all nine actors on stage, and each member of the audience.
Alan Jay Lerner began writing the screenplay in December 1949, and finished it in a 12-hour stretch in March(?) 1949 on the night before his wedding.
Irene Sharaff designed a style for each of the ballet sequence sets, reflecting various French impressionist painters: Raoul Dufy (the Place de la Concorde), Edouard Manet (the flower market), Maurice Utrillo (a Paris street), Henri Rousseau (the fair), Vincent van Gogh (the Place de l'Opera), and Henri de Toulouse-Lautrec (the Moulin Rouge). The backgrounds took six weeks to build, with 30 painters working nonstop.
A famous painter was hired to create the paintings that Gene Kelly displays on the streets of Paris.
A major reason Gene Kelly suggested Leslie Caron as the female lead was because he felt this movie needed a "real" French girl playing Lise, not just an American actress playing one.
A scene in which Gene Kelly dances and sings "I've Got a Crush on You" while in his pajamas was filmed but did not make final cut. Kelly created a similar number with the song "All I Do Is Dream of You" for his next movie musical, Singin' in the Rain, and it also ended up on the cutting room floor.
According to Leslie Caron, her introductory dance sequence, which included a seductive dance with a chair, was considered too suggestive by some censors. Gene Kelly directed the brief fantasy dance sequences shown as Lise is introduced.
After Arthur Freed and Ira Gershwin reached an agreement during their weekly pool game, film rights to George Gershwin's "An American in Paris - A Tone Poem for Orchestra" were purchased for $158,750, and Ira received $56,250 as a consultant to write any necessary new lyrics for songs used.
Despite the objections of Gene Kelly who wanted to shoot on location in Paris, the movie was shot at MGM Studios in California, on 44 sets built for the film. It was reportedly difficult for the studio to secure travel arrangements or locations for shooting. Two shots in the picture are from Paris, but they don't involve Kelly.
Even though Vincente Minnelli is credited as the sole director, he was sometimes tied up with his divorce from Judy Garland and other directing projects, leaving Gene Kelly to take over the directing duties.