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.
According to writer Ron Kivett, the monster has a leech-like mouth because it was originally supposed to suck the blood out of its victims.
Shot in 30 days.