They have the actor portraying Conrad Veidt as Major Strasser dressed in an SS uniform.
Major Strasser wore Luftwaffe uniform.
Early in the film, Curtiz approaches Dooley Wilson, who played Sam, on the Casablanca sound stage and is asked, "Good day, Mr. Curtiz. What will it be this morning?" And then he begins to play a tune on the upright piano. Dooley Wilson could not play the piano; he was a drummer. In Casablanca one can observe him patting the keyboard with two flat hands as he pretends to play.