The scene where the bar patrons sing "La Marseillaise" to drown out the Germans at Rick's was movie magic at its finest. The movie was shot in 1941 or 42, the extras were mostly actual French refugees, and the tears in their eyes are largely real.
Also, Conrad Veidt, who plays the Nazi commander, is one of my silver-screen heroes. He was a German actor who married a Hungarian Jewish woman and was very vocally anti-Nazi, smuggled his family out, and sent thousands of British kids chocolate and money while they were hunkered down during the Blitz. He would have become a much bigger name if he hadn't dropped dead on a golf course at 50.