As is typical of the era, Welles and Brent realistically appear two decades older after the prologue, but Colbert looks like she hasn't aged a single day.
Lucile Watson's name is misspelled "Lucille" in the opening credits.
Applying for a visa to enter the US, especially from a country already at war and in a sensitive war industry, his fingerprints would be checked and it would be discovered that he was an army deserter.