Peter Lorre's whistling was dubbed by director Fritz Lang. The tune that Peter Lorre's character whistles is "In the Hall of the Mountain King," from the "Peer Gynt" suite, by Edvard Grieg. Peter Lorre was Jewish and fled Germany in fear of Nazi persecution shortly after the movie's release. Fritz Lang, who was half Jewish, fled two years later. Contrary to popular belief, Fritz Lang did not change the title from "The Murderers are Among Us" to "M" due ...[Read Story ]