Nazi leader Adolf Hitler banned this film from release in Germany because of its strong anti-Nazi sentiments. In addition, all MGM films from that point until the end of the war also were banned in Germany because the studio made this one.
At the start, Professor Roth (Frank Morgan) is celebrating his 60th birthday. In fact, when Morgan filmed that scene, he was closer to his 50th birthday and, unfortunately, did not live to see his 60th. (He was born June 1, 1890, and died September 18, 1949.)
When this movie was made, America was not part of World War II. Most of the heads of the major studios in Hollywood were for American involvement in the war. This movie is one of a number made during the late 1930s and early 1940s that represented this belief. These films include A Yank in the RAF (1941), Man Hunt (1941), Foreign Correspondent (1940), Confessions of a Nazi Spy (1939) and Sergeant York (1941).
The last of four films pairing Margaret Sullavan and James Stewart; the other three are Next Time We Love (1936), The Shopworn Angel (1938), and The Shop Around the Corner (1940).