J. Carrol Naish's character of Dr. Durea first refers to Lon Chaney Jr.'s character as "Grodin," although his name in the film is actually "Groton." Afterwards, Naish gets it right from that point on.
When Judith picks up Dracula's one-eyed demon-headed ring at the end of the film, she has flashbacks to earlier events in it. However, the flashback of Rico comes from a scene in it that Judith was not present for.
The two small holes in the side of the Oakmoor Cemetery caretaker's neck are substantially smaller than Dracula's fangs.
The order of the exhibits in the Creature Emporium boardwalk attraction changes from scene to scene throughout the entire film.
Dr. Durea's use of the same injections of his blood serum alternately causes Groton to both transform into a savage, mindless killer and to be transformed back to normal.
When the Frankenstein Monster rips the door off of the car in the local Lover's Lane, it has no hinges on it.
When Judith is tied to a railing by Dracula, the ropes binding her to it are so loose that she could have easily escaped any time she wanted to.
Judith's name on the Las Vegas billboard and her name on the telegram she receives do not match.