Farley Granger had a difficult time with Tom Savini creating a cast of his face for the film. Granger was claustrophobic and Savini had to encase his entire head to make the plaster cast of Granger for the films finale. The process caused Granger much stress.
Director Joseph Zito once told a guard at a movie theater where the film was being screened, that he was the director of this film. To this the guard responded, "You really DID kill those people, right?".
On the audio commentary for the DVD director Joseph Zito said that he hated the props used for Rosemary's photo album and gravestone so much that he was apprehensive about even allowing the film to be released on DVD. Zito says he always felt the props were painfully fake-looking and avoided coverage on them as much as possible while shooting.
It took 18 takes of Cindy Weintraub being kicked in the face by the Prowler, before director Joseph Zito was satisfied that they had a good take. Fortunately, the foot that kicks her was a fake that was made of rubber.
According to the audio commentary, AVCO Embassy pictures made an offer of $750,000 for distribution rights to the film ("The Prowler" cost $1 million to produce). Director Joseph Zito states that the producer declined the offer and decided to self-distribute the film himself. A decision that Zito believes hurt the films box office.
The movie was filmed in the city of Cape May, New Jersey, and included the use of some of the city's Victorian buildings. The Colonial Hotel was the location of the dance scenes and dorm interior and the Emlen Physick Estate as the dorm exterior. The gazebo scene was filmed at the Cape May County Park. Also featured is a Victorian building which was abandoned at the time of filming, but has since been restored and is now operating as a guest house.
The trivia items below may give away important plot points.
Tom Savini actually did fire a double barreled shotgun into George Fraser's fake head to make it explode in the finale of the movie. Although you can't see it on screen, Savini said only half of the fake head was actually destroyed in the shot.
The shot of the Prowler placing a rose on Sherry's head while Pam is changing in the next room was originally shot as part of Sherry's brutal murder scene. It was edited into the film later on to create more tension for the scene in which Pam returns to the girls room to change.