Visible crew/equipment: Towards the end of the fairground scene, as Michael and Ellen are walking to the right, and just before the cop tells them one of the stolen bills has been passed to the dress shop, the shadow of the boom microphone is visible across the brick wall in the background. (00:22:20)
Revealing mistake: Inventor Dr.Tobel is shown with his bomb sight. Later in the film we see the same equipment, only this time it is Sherlock Holmes' ultraviolet light apparatus. (00:22:05 - 00:45:30)
Continuity mistake: Bela Lugosi offers John Berkes a cigar ("a real Havana"), but when he's relaxing, he calls him by his 'street' name, Fingers. The man nervously brings a hand to his collar, but at the cut Fingers' fingers are gone out of frame. (00:06:30)