Director Don Barton filled the monster role through a newspaper ad. The ad read: "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.
Originally, the film was supposed to include scenes of gigantic catfish destroying the countryside. Footage of the walking catfish on miniature landscapes was too hokey. One shot made it into the film; a catfish squirms next to a miniature fence during one sequence.
In an interview, writer Ron Kivett said the script was inspired by an article he read about a species of 'walking' catfish that could live in water and on land. The article theorized that the fish were possibly a mutation. Doctor Leopold refers to the same species of fish in his voice-over narrative.
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.
The budget on Zaat was so low that the production couldn't afford lighting for the night scenes outdoors. The headlights of cars had to be used to light night scenes. The reflection of the car lights can occasionally be spotted in windows as the monster walks the deserted streets.
The monster costume had to be repaired on a daily basis during shooting, according to writer Ron Kivett. Kivett created the monster suit and had to continually add to it to cover damages to the suit during filming. It became quite heavy toward the end of shooting because of the frequent patching.
The monster suit was quite cumbersome for star Wade Popwell. The suit weighed 120 pounds and stood seven feet tall with 6'5'' Popwell wearing it. At times cuts had to be made during the shooting of swamp scenes when the monster's head would crash into unseen tree branches.
In the original script the monster was suppose to throw a chair through the window of the drugstore during his OD rage. However, the production couldn't afford to break a window so it was left out of the film.