Factual error: It is barely credible that a young Victorian woman like Elena would even think about wearing a goatskin miniskirt - exposing her legs in those days would be akin to walking about topless nowadays. Even if she did those bright yellow cotton knickers - gleefully visible in the scene in the beehive - are in no way from the 1860s. Her pants are a hundred years ahead of their time.
Continuity mistake: The police that come to the aid of the professor are driving an older Ford when they approach than when they arrive to help. The car is a newer model in the later scene.
Audio problem: As Tom and Mary exit a home that faces the town square, the sound of applause is heard even though almost all the townspeople are holding glasses of lemonade and nobody is clapping.
Character mistake: The registration number of the stolen van is GPW729 but every time it mentioned in the dialogue it is stated as GPW927.
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)