When "Gloves" Donahue (Humphrey Bogart) shows the desk clerk the newspaper with his mug on it, it's actually a picture of him as Roy Earle from La Grande Évasion (1941).
Phil Silvers and Jackie Gleason owe their presence in this movie to the direct intervention of Jack L. Warner, who personally phoned Director Vincent Sherman to ensure that they were added to the cast.
The scene in which "Gloves" Donahue (Humphrey Bogart) and Sunshine (William Demarest) confuse a room full of Nazi sympathizers with doubletalk was not part of the original script, but was invented by Director Vincent Sherman, who filmed it despite the objections of Executive Producer Hal B. Wallis. Wallis ordered it removed from this movie, but Sherman left a small segment of it in, and when preview audiences reacted positively to it, Wallis backed down and told Sherman to put the entire scene back in.
The Norwegian title for this movie translates to "Bogart Cleans House" or "Bogart Saves the Day".
George Raft and Olivia de Havilland were originally assigned to this movie in 1941, but Raft turned the role down. As with La Grande Évasion (1941) and Le faucon maltais (1941), Humphrey Bogart benefited from Raft's refusals.