Werner Krauss (Caligari)
Krauss was an unapologetic anti-Semite who supported the Nazi party and its ideology. In 1933 Krauss joined the Vienna Burgtheater ensemble to perform in Campo di Maggio (German: Hundert Tage), a drama written by Giovacchino Forzano together with Benito Mussolini, where-after he was received by the Italian dictator and also made the acquaintance of German Propaganda Minister Joseph Goebbels.
Conrad Veidt (Cesare)
Veidt had long been known in German theatrical circles as a staunch anti-Nazi. His activities came under the scrutiny of the Gestapo, and a decision was made to assassinate him. Veidt found out about the plot, and managed to escape Germany before the Nazi death squad found him . . . When Britain went to war, he gave most of his estate to the war effort. He also donated a large portion of the salary from each of his movies to the British war relief, as well.
Previously, I was most familiar with Veidt as Jaffar in The Thief of Bagdad, a villainous role which he played delightfully. He made me a fan.