It's like The Beatles: the more you know, the better it gets. This from The New Statesman (via The Browser), an article worth a read in its entirety at https://www.newstatesman.com/cultur...t-over-and-over-again-how-casablanca-was-made: "Nearly all of the 100-plus actors and actresses in the film were immigrants hailing from more than 34 different nations. Bogart was the lone American; you also had Bergman (Sweden), Claude Rains and Sydney Greenstreet (England), Paul Henreid (Austria), Conrad Veidt (Germany) and Peter Lorre, originally from Slovakia by way of London, who said that, like Brecht, he had changed countries “oftener than our shoes”. Hungarian SZ Sakall, who played the head waiter, lost three sisters to the concentration camps. "The director Michael Curtiz, himself a Hungarian Jew, cast them all personally, incorporating some of their stories into the movie: the trading of jewellery for exit visas, the presence of pickpockets. There were so many German Jews playing the very Nazis they had fled that German was frequently spoken on set, which was known as the International House. When the time came for the scene in which Victor Laszlo defiantly sings “La Marseillaise”, one character actor noticed everyone was crying: “I suddenly realised they were all real refugees.”"