Jacques Tourneur never planned to show the monster, but to leave it instead to the audience's imagination. However, the studio insisted that the monster be shown, and added it in post-production, allegedly without Tourneur's consent, approval or involvement.
In the movie "The Burbs", Tom Hanks' character (Ray) is in his basement with the paranoid neighbor (Art) who is trying to convince him that the Klopeks next door are actually Satanists. When he shows Ray an old book to make his point, take a look at the title and especially the author. "The Theory and Practice of Demonolgy" is supposedly written by none other than Julian Karswell. Someone....perhaps a writer, the director or the props manager was apparently out to pay homage to Curse of the Demon.
Beginning in the 1980s, Columbia Pictures replaced their edited 83-minute U.S. version with the uncut original 95-minute version while retaining the U.S. title "Curse of the Demon." The various video releases, and pay-tv showings, have used this restored version. A DVD release contained both versions.
This film was mentioned in the opening song from The Rocky Horror Picture Show (1975) ("Science Fiction Double Feature"): "Dana Andrews said prunes gave him the runes, but passing them used lots of skills".
The source story for this film, "Casting of the Runes", was also adapted into a radio play of that name for the anthology radio programme "Escape". The story was also adapted twice for British television, first as an episode of the anthology series "Mystery and Imagination" in 1968, and again as an episode of "ITV Playhouse" in 1979.
There is a possible reference to Citizen Kane when Holden (Andrews) breaks into Karswell's attic, which contains a wooden sledge. Indeed, Holden knocks it over, as if to draw more attention to it. It's not present in Ken Adams' production designs for the "room of junk".