According to the audio commentary on the 2000 Anchor Bay DVD, some of the substance props or stand-ins for the real Stuff used in the movie included lots of Häagen Däzs ice-cream, yogurt, and for one scene involving an enormous avalanche-like effect of Stuff crashing though a wall, fire-extinguishing foam. Other shots, such as the ones of the giant lake of Stuff, required superimposed images and animation.
According to Larry Cohen himself, in some scenes in which the Stuff chases characters, a foam made of blended fish bones was used. It stank so much that, as soon as the shots were done, the actors ran to a river in order to bathe and get rid of the stench.
Clara Peller reprises her role in a parody of Wendy's "Where's the Beef?" advertisements, asking instead, "Where's the Stuff?"
The original cut of the film was said to be much longer and described by Director Larry Cohen as more "dense and sophisticated." Feeling that the film was too long, it was cut to increase the pace of the film. There was a romantic scene between Moriarty and Marcovicci that took place in a hotel room in the original cut. In 2021, this long lost cut had apparently been found.
Chocolate Chip Charlie was inspired by Famous Amos cookies.