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 High Sierra (1940).
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".
When "Gloves" Donahue ((Humphrey Bogart)) and Sunshine (William Demarest) take the sidewalk elevator down to the basement of the toy warehouse (after taking the IDs off of the real saboteurs from Detroit, Michigan), they show the cards to a man outside of the meeting room. The heading of the card reads "Gesangverein Aurora", which translates to "Aurora Singing Club".