The amount of sea worms used in the film was countless, as the production would order shipments of 250,000 Glycera worms at a time. The production would end up wiping out the New England fishing industry's supply of Glycera worms that year.
The inspiration for the film came from a childhood experiment between director Jeff Lieberman and his brother. One evening the two hooked up a train transformer to wet soil and used the electricity to drive hundreds of worms out of the ground. Young Lieberman noticed that the worms tried to get away from the glare of the flashlight that the boys were using to see by because worms are sensitive to light. It became the scientific basis behind this film and the story of the experiment is re-told by the character of Roger Grimes.
On the Region 1 DVD commentary of the film, director Jeff Lieberman says that the old farmhouse used for Mr. Beardsley's home during the shoot is known as one of the most infamous haunted houses in Georgia.
During the film's production, there was a mix-up with the film processing lab. Film footage from a wedding was accidentally sent to director Jeff Lieberman and B roll footage of the worms used in the film was accidentally sent to the newlyweds.
The shot of the worms pouring out of the living room ceiling in the film was actually a reverse shot. The camera was turned upside down and filmed live worms being dropped onto a floor that was a mock-up of the ceiling. When the footage was reversed, it appeared as if the worms fell out from a hole in the ceiling.