Mary Shelley: It's a perfect night for mystery and horror. The air itself is filled with monsters.
The Monster: We belong dead!
Dr. Pretorius: We shall drink to our partnership. Do you like gin? It is my only weakness.
Dr. Pretorius: To a new world of gods and monsters!
When filming the scene where the monster emerges from the burnt windmill, Boris Karloff slipped and fell into the water-filled well. Upon being helped out, he realized he had broken a leg in the fall. The metal struts used to stiffen his legs (for the famous "monster lurch") helped keep the bones in place until they could be properly set.
The "body count" in the original cut was 21. This was trimmed to 10 after pressure from the censors.
When the castle is self-destructing, the Doctor can be seen against the far wall. Yet he is next seen outside in the arms of his beloved, watching the explosions. There were two endings originally: the first had Doctor Frankenstein dying within the castle and this was filmed. But the producers judged this a bit harsh and wanted a happy ending, so they shot the extra footage (too expensive to re-film the explosions).
The musical soundtrack for this film proved so popular, it was used again in the Flash Gordon serials starring Buster Crabbe.
Shot in 46 days at a cost of approximately $400,000. Boris Karloff sweated off 20 pounds labouring in the hot costume and make-up.
DVD Easter Eggs: (Hidden So You Don't See Anything You Don't Want To See)