Continuity mistake: Lobo has a very distinct scar on his cheek in the beginning and end of the movie. However, just after Dr. Strowski has entered the house, Lobo is seen coming down the stairs, and his scar is completely gone.
Continuity mistake: When Cpt. Lawton is talking to the secretary at the newspaper, the pencil stuck behind her ear keeps disappearing and reappearing. It is there when the secretary is seen from behind, and is gone every time we see her face.
Continuity mistake: When Dr. Strowski approaches the door to the house in the swamp, the door is a dark color with a circular ornament in the middle and only two panels. When the same door is seen from inside the house (the door opens inward), it is a light color, with five panels and no ornamentation.
Continuity mistake: In the beginning of the movie, we se Lobo chasing off the two hunters. Lobo is then standing outside in the torrential rain, but when he walks into the laboratory a few seconds later, he is completely dry.
Continuity mistake: When Dick is pushing the boulder on to Dr. Vornoff, it is night time and pitch black. Except in the close-ups of Dick, then the background is much lighter, as if it was morning. A second later (when the camera goes to a long shot), it is completely dark again.
Revealing mistake: Every time the octopus kills someone, it is painfully obvious that the octopus is fake, as it never moves. The actors are only lying on top of it with a couple of tentacles wrapped around them, and thrashing about to make it appear as thought they are being killed. It never really works.
Factual error: When Dick has fallen into the hole in the swamp and is shooting at alligators, he manages to fire eight shots from a six-shot revolver.
Continuity mistake: After Janet has crashed her car in the swamp, you can see a snake in the tree next to her. In long shots, the snake is a light color, and is completely immobile. In close-ups, the snake moves and is a darker color. Also, when Lobo finds Janet, the snake is back to its original position, even though we saw it starting to crawl down the branch it was on.
Revealing mistake: During the fight between Dr. Vornoff and Lobo, Lobo is being thrown through the doorway of the lab and grabs the wall to steady himself. The whole wall bends, as though made of plywood.
Revealing mistake: When Dr. Vornoff has been subject to his own machine, and has gained "the strength of 20 men", you can easily see the platform shoes worn by Bela Lugosi's stunt double to make him bigger than Tor Johnson. Dr. Vornoff did not wear these shoes when he was strapped to the table, they only appear after he gets up.
