The film is regarded as being one of the first slasher films. It set the layout for films such as John CarpenterHalloween (1978). However, director Bob Clark considered it to be more of a psychological horror film than a slasher film.
In 1986, Olivia Hussey met producers for the film Roxanne (1987), since they were interested in casting her for the title role. Roxanne co-star Steve Martin met her and said "Oh my God, Olivia, you were in one of my all time favorite films." Thinking it was Romeo and Juliet (1968), Olivia was surprised to find out it was actually Black Christmas (1974). Martin claimed he had seen it over 20 times.
The film had only moderate box office success and negative critical reception when originally released, however the film went on to have a large cult following. It has since received a critical reevaluation and is now considered a classic.
Upon initial release in the US the films title was changed to "Silent Night, Evil Night" because the American distributor feared the title "Black Christmas" might cause the film to be mistaken for a 'blaxploitation' flick. However the film didn't do well under the new title and it was changed back to the original "Black Christmas" title, under which it was a success.
The original title of the films script was "Stop Me". It was director Bob Clark who came up with the title "Black Christmas" saying that he liked the irony of something dark occurring during such a festive holiday.
Composer Carl Zittrer said in an interview that he created the bizarre music score for the film by tying forks, combs, and knives to the strings of his piano so the sound would warp as he struck the keys. Zittrer also said he would distort the sound further by recording audio tape while putting pressure on the reels of the machine to make it turn slower.
According to director Bob Clark the original script for the film featured murder scenes that were more graphic. Clark however felt that it would be more effective if the murders were toned down and made more subtle on screen. Writer Roy Moore liked the idea as well.
Director Clark claims that he re-wrote half of Roy Moore's script, adding some humor into the film. Moore was also against the idea of never seeing the killer however when he saw the finished film, he was very pleased with it.
There is a purpose for the eerie ringing telephone as the closing crawl appears. This indicates that the main heroine will die. However, the heroine's death is left open to personal interpretation by each member of the audience. The ending of tbe film forces people to think independently.
During an interview with director Bob Clark, Clark said Olivia Hussey's decision to take the role of Jess was based upon advice given to her by a psychic. According to Clark, Hussey said her psychic believed that the film would be successful and a wise career choice for her. She took the role.
The role of Lieutenant Fuller was originally supposed to be played by Edmond O'Brien, but due to failing health from Alzheimer's he had to be replaced. John Saxon (who was originally considered for the role) was brought in at the last minute when a space in his schedule opened up.
The snow seen outside of the sorority house was actually fake, because there had been surprisingly little snow fall during the filming. A foam material that was provided by the local fire department was used for snow on the lawn and according to cinematographer Albert J. Dunk the substance actually caused the grass on the lawn to grow greener than ever the following spring.
Minimal vulgarity from the phone calls were initially scripted, director Bob Clark read out rather tame dialogue for the actors to react to. However stronger coarse language was later looped in post-production for a stronger reaction.
Despite its ominous themes and plot, Olivia Hussey reassured that the set was a very light and happy place between takes stating everyone got along with each other very well. She did however admit that Margot Kidder was rather distant from cast/crew during the filming.
The audio for the demented phones calls was edited into the film during post-production. While shooting the footage for the phone call scenes the actresses were actually just reacting to threatening dialog being spoken from director Bob Clark from off-camera.
Cinematographer Albert J. Dunk created Billy's POV shots by rigging up a camera harness that would mount the camera on his shoulder as he walked about the house and climbed the trellis and attic ladder himself.
The trivia items below may give away important plot points.
After seeing the ending of the film, studio executives asked director Bob Clark to change the ending. The proposed idea was to have the cops leaving Jess alone with Chris, Claire's boyfriend. She wakes up and he says, "Agnes, don't tell them what we did." Then he kills her. However, Clark refused and insisted that the ending be ambiguous.
Bob Clark stated in an interview that he couldn't recall whose eye was used for that infamous shock scene where Jess sees "Billy" staring at her from behind the door. It was possibly Albert J. Dunk, the camera operator who played Billy during some of the murder scenes, but it has never been confirmed just whose staring eye has given countless viewers nightmares for all these years.
Billy" is mainly embodied by camera operator Albert J. Dunk, who not only did the POV shots from the killer's perspective, but also played him during a few of the murders. It was his hands that were seen by the audience. Nick Mancuso, the main voice actor as "Billy", was not on set. Both director Bob Clark and Keir Dullea confirmed that Dullea at no point contributed to "Billy".