Erika Carlsson played the nurse as well as the topless possessed woman at the beginning of the film, even though she was only credited as Nurse Morgan. She holds the rare distinction of being killed twice as different characters in a single movie.
Alfredo Zacarías got the idea for this film from a conversation with a psychiatrist friend on split personalities.
Alfredo Zacarías initially wanted Roger Corman to pick this film up for a theatrical release, but ultimately decided to distribute this movie himself.
The movie was featured on the German series Die schlechtesten Filme aller Zeiten (2013) ("SchleFaZ"). It was aired April 2021 on German TV station Tele5. In the series, two hosts present the whole flick - and make fun of it throughout the movie.
Academy Award winning screenwriters Quentin Tarantino and Roger Avery (Pulp Fiction) review "Demonoid" in Season 1 Episode 4 of their 'Video Archives' podcast, to much acclaim.