Plot hole: Maria describes in lurid detail how Anna was arrested by the Germans and tortured by being severely whipped, leaving her with gruesome scars all over her back. She also says that Anna hasn't spoken a word to anyone since she escaped from captivity. How, then, does Maria (or anyone else) know about the scars? Nobody saw them (they don't exist) and Anna obviously didn't tell anyone about them.
Revealing mistake: The sea creature Gorgo is paraded through the streets of London on a flatbed tractor trailer, and an off-screen American newsman announces the monster's arrival at Battersea Park, where it will be exhibited at Dorkin's Circus. The announcer introduces the creature's owners as they step from their motorcade, saying, "And our own Mr. Dorkin, of Dorkin's Circus, in the checkered suit." Problem is, Mr. Dorkin is wearing a plain gray flannel suit. Closeup shots of Mr. Dorkin over the next 40 seconds reveal that the suit is not checkered, not plaid, not striped, not patterned in any way at all. It's simply a plain gray suit. Apparently, the announcer's pre-recorded lines were never modified after changes were made in costuming. (00:34:05 - 00:35:00)