An American In Paris is an integrated musical, meaning that the songs and dances blend perfectly with the story. The film was inspired by the 1928 orchestral composition by George Gershwin.
The story of the film is interspersed with show-stopping dance numbers choreographed by Gene Kelly and set to popular Gershwin tunes. Songs and music include "I Got Rhythm," "'S Wonderful," and "Our Love is Here to Stay". It set a new standard for the subgenre known as the "songbook" musical with dozens of Gershwin tunes buried in the underscore. The climax is "The American in Paris" ballet, an 18 minute dance featuring Kelly and Caron set to Gershwin's An American in Paris, featuring an Impressionistic period daydream in the style of various painters, is one of the longest uninterrupted dance sequences of any Hollywood film. The ballet alone cost more than half a million dollars, a staggering sum at the time.
It's funny to think of such a work of art being born over a pool game between film producer Arthur Freed (SINGIN' IN THE RAIN, WIZARD OF OZ, ON THE TOWN, MEET ME IN ST. LOUIS and THE BAND WAGON) and Ira Gershwin. It was Freed's idea to buy the title so he could use if in a film about Paris and Gershwin's idea that it would only use Gershwin music.
Original cast was to have Cyd Charisse but she discovered she was pregnant before shooting began. 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. Gene Kelly discovered Leslie Caron while vacationing in Paris where he saw her perform in a ballet. When she got the call to audition, she said, "Who's Gene Kelly?" 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.
Vincente Minnelli first wanted Maurice Chevalier in the Georges Guétary part, and 'Celeste Holm' in the 'Nina Foch' part.
Minnelli was a groundbreaking director of musicals with Meet Me in St. Louis (1944), An American in Paris, and The Band Wagon (1953). He used color and songs in ways they hadn't been used before. He used space and time imaginatively. Best of all, though, he allowed himself to cut loose for the long ballet sequences that end all his movies. The ballet in An American in Paris may be his best work.
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.
Other highlights include Guetary's rendition of "Stairway to Paradise"; Oscar Levant's fantasy of conducting and performing Gershwin's "Concerto in F" (see why it was Oscar Levant's favorite.)
The ballet sequence, now that we know it was successful everybody now wants to take credit for it, Freed, Minnelli, Kelly but before the film was completed the New York office of MGM said no to spending a half million dollars on a ballet. So Freed went to studio head Louis B. Mayer himself and got him to agree, New York said no. Finally Gene Kelly showed the New York office how a British film, THE RED SHOES used a long ballet sequence and that film became a world wide hit  and is still considered today the premium example of a successful art film. Well the financial guys finally gave in and signed the checks.
There was a break in production after 1 November 1950, at which point Gene Kelly began rehearsing the ballet choreography. By the time production for that final sequence resumed on 6 December, Vincente Minnelli had finished directing another film - Father's Little Dividend (1951).
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.
Roger Ebert said after viewing the recent restoration, "An American in Paris has many qualities, not least its famous ballet production number, with Kelly and Leslie Caron symbolizing the entire story of their courtship in dance." An American In Paris is often compared to SINGIN' IN THE RAIN as to which it the greatest musical ever made, and one critic put it best when he said, "SINGIN' IN THE RAIN makes me happy and An American In Paris makes me feel good." The ballet represents Kelly's fantasies as depicted by the great French artists (Renoir, Rousseau, Lautrec, Dufy) he admires. Arranging a screening for the then ailing Raoul Dufy, the actor and producer ducked out until the end credits. There, relieved, they found the artist, moved to tears, requesting a second helping of the sumptuous finale.
The film was also the first to win a Golden Globe award for Best Motion Picture (comedy or musical.)
Gene Kelly received an honorary Academy Award that year for "his versatility as an actor, singer, director and dancer, and specifically for his brilliant achievements in the art of choreography on film." It was his only Oscar.

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Unremittingly bleak, this film sets out to produce (I'm guessing) a modern small town American Christmas fable in the Capra style. If fails....completely and absolutely fails. I've been trying to think of one good thing about it and can't. Let me mention some of the highlights ...
People don't die, they get to spend eternity as immigrant workers in Santa's factory. Angels are actually ex-cowboys who sit in trees. Santa can bring people back from the dead (if you send him a nice letter).
And the plot.. I won't spoil it for you but there has to be some light in films if only to contrast with the darkness but there isn't any. Even the photography is bleak - snow shown at the end of a freeze, everywhere looking cold, damp and miserable.
As you might guess, the film has a happy (schmaltzy) ending. What a relief !