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Factual error: The movie is set in Transylvania, but the natives all speak German and with German accents (probably an homage to the book, but still incorrect). (00:14:30)

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Revealing mistake: One of Peter Boyle's teeth on his lower jaw was painted black for that "broken grin" look. It can be seen reflecting in some scenes: when Frankenstein enters the cell with the monster and it cries, and later when the monster screams while killing the jailer. (01:15:30 - 01:28:40)

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Continuity mistake: When Frankenstein releases the monster from the experiment bed, he reaches for the third bar (over the monster's thighs) first, but the fourth bar (over his lower legs) is already open. All of them were closed when they left the monster in the lab. (00:46:50 - 00:53:55)

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Audio problem: As Frankenstein lures the monster back to the castle with the violin, if you watch very carefully, some of his bow movements don't match the length of the sound that is heard. (01:35:30)

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Continuity mistake: The brain that Frankenstein draws on the blackboard in the first scene is different from the one behind him as he is seated and lecturing. Check the shading on the brain stem. (00:05:55 - 00:09:35)

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Trivia: The original cut of the film was three times the length of the final cut.

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