Parker Brothers wouldn't let the filmmakers use their Ouija board in the movie, so director Roberta Findlay had to come up with the stone spirit hand instead.
The role of Farkas was originally written for a man. Pam La Testa came to the audition with her boyfriend and introduced herself to director Roberta Findlay. Findlay was so impressed by La Testa that she cast her in the part.
When the lights begin to flicker in the living room, the couple's book shelf is shown. A copy of William Peter Blatty's Legion can be seen on the shelf. Legion is the sequel to The Exorcist.
The film was a lot more graphic in its original cut, but these scenes were removed due to interference from the MPAA.
Several crew members also act in this film as asylum inmates.