* ActorInspiredElement:
** Peter Jason came up with the idea for the mouth trumpet routine.
** Jameson Parker came up with the idea for the card trick.
* AwesomeDearBoy: Music/AliceCooper is in the movie primarily because he's a huge fan of horror films and he (as a very devout Christian) was highly interested in the film's portrayal of Satan.
* BasedOnADream: The genesis of the project came from Debra Hill describing a dream she had of a vague dark figure exiting a church which filled her with dread. Creator/JohnCarpenter developed the story around this idea in hopes of recreating the fear Hill really felt.
* InspirationForTheWork: Creator/JohnCarpenter became inspired while researching theoretical physics and atomic theory. He recalled, "I thought it would be interesting to create some sort of ultimate evil and combine it with the notion of matter and anti-matter."
* PlayingAgainstType:
** Creator/DonaldPleasence was primarily known for playing coolly cynical, even cruelly manipulative characters, but his priest here is [[spoiler: horrified at the deception the church has played on the world]]. Similarly, Victor Wong's roles are typically very religious or otherwise steadfast in their ways, such as the mystic Egg Chen in ''Film/BigTroubleInLittleChina'', but Birack is open-minded and accepting of wildly different perspectives.
* ProductionPosse: Donald Pleasence, Victor Wong, and Dennis Dun had all worked with Carpenter before. Cinematographer Gary Kibbe and actor Peter Jason both became Carpenter regulars beginning with this film.
* PromotedFanboy: Music/AliceCooper is a big horror fan.
* ThrowItIn: When Dr. Leahy introduces himself to Dr. Birack, Peter Jason wasn't expecting Victor Wong to walk away in the middle of the scene. Jason's subsequent confused appearance and awkwardness is natural and unscripted.
* YouMightRememberMeFrom:
** Music/AliceCooper plays one of the possessed hobos (his character is called "Street Schizo" in the end credits).
** Creator/JamesonParker and his glorious PornStache is best known for starring in ''Series/SimonAndSimon''.
----