Lesleh Donaldson was doubled by a figure skater for the skating sequence on the pond. Donaldson was originally going to do this sequence herself and even had undergone training in a skating arena to do her own skating routine, but fell down on the bumpy ice on the day this scene was shot and cut her chin. Moreover, Donaldson's skating double also played the killer in that same sequence.
Céline Lomez was originally cast in the role of Brooke Parsons. However she was replaced by Linda Thorson after a brief time on the production. For years afterward there were rumors that Lomez was replaced because she refused to do a nude scene, however producer Peter R. Simpson said in an interview with TerrorTrap.com that Lomez was really replaced because they weren't impressed by Lomez's acting skills. The issue of nudity had no part in the decision.
Shooting of the film started in 1980 but the production was plagued with problems. It was shelved for over a year during which re-writes, re-shoots, and at least one re-casting was done. The film was finally completed and released in 1983.
The trivia items below may give away important plot points.
The climax as originally filmed had Patti performing her stand-up comedy routine on a stage with the bodies of her victims. This scene was eventually changed in a reshoot to Patti pretending to perform her routine in the asylum in front of the inmates instead.
During an interview with TerrorTrap.com, producer Peter R. Simpson said that originally Matthew's death was suppose to be on-screen. Matthew was suppose to be killed while riding a snowmobile, which then would have crashed through a bay window into the library frightening Tara. However the scene was re-written to where Stryker and Brooke's bodies crash through the window when they fall from a second floor window after being shot.