Black Christmas

Andrea Martin, who played Phyllis in Black Christmas (1974), said in an interview that she hadn't thought about "Black Christmas" for 32 years and it "came out of the blue" when Glen Morgan offered her the role as the house mother in the movie.

Melissa explains to Heather that Billy is not a serial killer because he didn't murder for sexual thrill and is instead a spree killer because he lost his mind. She's not entirely correct, the only difference between a spree killer and a serial killer is the lack of a "cool-off" time. A spree killer is someone who kills multiple people at one time or in quick succession while a serial killer is someone who kills multiple people in distinct incidents. Although Melissa is right that Billy is a spree killer, she doesn't have the correct reasoning.

The final credits include the message "Goodbye, Shirley," in tribute to composer Shirley Walker, a frequent collaborator with director Glen Morgan. Walker passed away in November 2006, before "Black Christmas"' release.

The European version features different and more violent kills and the complete hospital showdown has been re-cut completely.

• In the European version Billy dies on an operating table as doctors try unsuccessfully to revive him.
• Leigh (Kristen Cloke) is taken to the morgue to ID Agnes and finds Clair's (Leela Savasta's) remains in the body bag marked for Agnes. Leigh returns to Kelli's ('Katie Cassidy''s) room to find Agnes hiding in the bed pretending to be her. Agnes attacks Leigh and snaps her neck. Kelli returns from getting X-rays done, is attacked by Agnes and kills her by shocking her to death with a defibrillator.
• Kelli is picked up by her parents and leaves the hospital and the camera zooms in on a PEACE ON EARTH sign hanging on a door.
• In the US version Billy drops down through a ceiling tile after Agnes is killed and chases after Kelli. Kelli breaks the window to her room and runs out into the hallway with Billy close behind. He fights with her before ending up falling over a railing and being impaled on the star on top of a Christmas tree in the lobby below.