During filming, Director Gary Sherman purposely avoided letting the color red be visible in any scene, so the sight of blood during the murder sequences would be all the more shocking. Sherman even went as far as to have the taillights of vehicles replaced with purple lights, instead of the normal red.
This was Jack Albertson's final theatrical film (although he filmed another made-for-television movie the same year he died). In poor health, and suffering from cancer all through filming, Albertson passed away a few months after this movie's release. He nonetheless lived long enough to see it at its world premiere in Hollywood, in which he attended in a wheelchair with an oxygen tank and mask.
Melody Anderson's reactions to being shot were very authentic. One of the squibs set to explode under her dress actually flew upward very close to her ear and gave her a scare, it also caused her to lose hearing in her right ear for a few moments.
Gary Sherman intentionally chose foggy weather conditions, in which to film, while on-location in California. The film's setting is suppose to be Maine, and the locations looked most like northern New England when the weather was foggy. In addition, Sherman liked the ominous mood the gloomy weather created.
Stan Winston's special effects went beyond creating gore for the film. The figure in the full body cast lying in George LeMoyne's hospital bed was a mechanical dummy built by Winston. The life-like detail and elaborate movements the dummy was rigged to make gives the appearance that its a real person and makes the infamous needle-eye stab all the more startling.
Due to child labor laws, the filmmakers could not get permission to use the boys who played Jamie at night. Because the kids' entire part took place at night, a huge tent was constructed that completely covered the family car and the haunted house, making it look like it was nighttime underneath it. To properly ventilate inside the tent so that the cast and crew could breathe, fans were set up. But they made so much noise, that the live sound that was recorded during filming was unusable. So all of these scenes had to be dubbed by the actors and actresses in post-production. This is why Nancy Locke's mouth is frequently moving when she's not talking.
The film suffered a lot of interference from PSO International, the third financer who bought out the second financer, Aspen (who in turn had bought Guinness, the original financer). PSO wanted to emphasize gore over comedy, the latter, on which Gary Sherman's Director's Cut had concentrated. As a result, numerous scenes were cut or shortened, and two scenes of graphic violence were tacked on at PSO's request: the killing of the drunk fisherman (Ed Bakey) and the acid death of Doc (Joe Medalis). The death of the fisherman (which was originally an off-screen kill in the first cut) was done by Stan Winston, but they could not get Winston back to off the doctor (which was not in the first cut at all, as he was supposed to be dead already), so another special effects team was used on that one sub-par effect.
On the day when the opening beach scene between Freddie (Christopher Allport) and Lisa (Lisa Blount) was shot, the weather conditions were too beautiful for Gary Sherman's liking. The crew constructed a huge flag to hang from a rigging on a cliff overhanging the beach to block most of the sunlight out, so the scene could be shot with the film's dim atmosphere.
The effects team, who created the "dissolving head" effect for Doc's murder, mentioned in an interview that Gary Sherman had originally told them that he wanted to do the scene in one unbroken shot, meaning they had to build a head that was both convincing, and also would "melt" the way they wanted it to. They lamented the fact that, while they did the best they could with what they had, Sherman ended up using a cutaway shot anyway, which would have given them the opportunity to make the scene much more realistic.
The shot where Paul Haskel (Robert Boler) pulls into the gas station next to Sheriff Dan Gillis (James Farentino) was shot from inside Dan's Jeep, and required the crew to build a track across the inside of the vehicle for the camera to move.
In a 1983 interview with Starburst promoting Blue Thunder (1983), Dan O'Bannon disowned this movie, claiming that Ronald Shusett had actually written it by himself, but needed O'Bannon's name on the project, promising he would implement some of O'Bannon's changes. Upon seeing the finished film, O'Bannon realized that Shusett hadn't included his material, but it was too late for him to take his name off the credits.
The scene where Janet comes home and speaks to Dan briefly, was done in one long, elaborate tracking shot. The shot began with a gigging that attached the front door of the Gillis house to the camera. The camera captures Janet pulling up, pulls back as she approaches, and the crew quickly bolts the door in the door frame (detaching it from the camera rigging). The shot then continues to pull back revealing the door as Janet opens it, then follows her as she enters the living room and speaks to Dan. Then it was suppose to continue to a front window where we would see Janet leave again (though this bit was cut from the film).
The trivia item below may give away important plot points.
The films was re-edited numerous times throughout the production. Originally, the attack on the family occurred later in the film, after the hitchhiker's murder, which is why the resurrected hitchhiker can be seen among the attackers during the scene with the travelling family in the old house.