Don Barton filled the monster role through a newspaper ad, "Wanted: 6'5" or taller male to play the role of monster in horror movie. Must be experienced swimmer, scuba diver. Acting Ability not required!" Barton said ten people responded.
The production couldn't afford lighting for the night scenes outdoors. Car headlights were used to light night scenes. The reflections are occasionally visible in windows as the monster walks the deserted streets.
In the original script the monster was supposed to throw a chair through the window of the drugstore during his rage. However, the production couldn't afford to break a window, so it was left out of the film.
The Marineland park location used for Dr. Leopold's lab was previously used for La Revanche de la créature (1955).
The orchestral music score occasionally heard during the movie is actually an old stock film score. It's been featured in such B horror films as "The Brain That Wouldn't Die" and, most curiously, a news reel segment about the Palm Sunday tornado outbreak in 1965.