An Affair to Remember is a remake of the film Love Affair. Both are directed by Leo McCarey. In the original Terry McKay was played by Irene Dunne. The year before An Affair to Remember was made Deborah Kerr played Anna Leonowens in The King and I. Irene Dunne played the same role in Anna and the King of Siam, of which The King and I is based.
Cyd Charisse discovered she was pregnant during pre-production of An American in Paris and Leslie Caron was brought in to replace her by Gene Kelly. She had been malnourished during World War II and since it was her first film she was not used to the long schedule, so she would tire easily and could only every other day.
Gene Kelly was a major part of production on An American in Paris. Originally he pushed MGM for the film to be made in Paris (this did not happen), he also gave Leslie Caron her part in the film after seeing her perform a ballet in France, and as he did in almost all of his films he choreographed the dances for the film.
During one of their weekly pool games game Arthur Freed and Ira Gershwin made an agreement on the price for the rights to George Gershwin’s An American in Paris-A Tone Poem for Orchestra. The film rights were bought for $158, 750 and Ira received $56, 250 to be a consultant to write any new lyrics for the songs (if they needed any).
The scene in which Sky (Brando) and Nathan (Sinatra) first meet was filmed numerous times. They had to stop after Frank Sinatra said he could not eat another bite of cheesecake. Marlon Brando knew Sinatra did not especially like cheesecake and purposely messed up his lines every time that day. Then the next day he did the scene perfectly on the first take.
The role of Adelaide in Guys and Dolls also caused much fuss. Marilyn Monroe reportedly wanted the role, but Joseph L. Mankiewicz didn’t want to work with her again after their experience together on All About Eve. Betty Grable, Grace Kelly and Judy Holliday were all considered for a brief period of time. Finally Vivian Blaine won the role.
(Source: classicmovietrivia)
Frank Sinatra, Gene Kelly, and Clark Gable were all original choices for the role of Sky Masterson in Guys and Dolls before Marlon Brando. Sinatra wanted the role badly and contested the decision to cast un-musical Brando. As almost a consolation prize Sinatra was cast in the role of Nathan Detroit.