Casablanca began as a stage play called Everybody Comes to Rick's and ended winning best picture, best director, and best adapted screenplay.

The writers, after winning the Academy Award, dismissed the original writer's claim that their script, basically, just copied his play.

Though, if you are familiar with the play, much of the story and dialogue did come from the original stage play.

However, Julius and Philip Epstein and Howard Koch, the Hollywood writers, did significantly improve the story. They changed the characters from crude and common to high-class and noble. They punched up the dialogue and added numerous comedy vignettes. They toned down the blatant sexuality and emphasized the romance. Or maybe this was just the censorship of the Production Code.

They introduced a classic theme: when you love someone who doesn't love you, it's soul-crushing. And when you realize they do love you; you are filled with a powerful force for good.

Julius Epstein called this 'corn'. "But when corn works, there's nothing better."