- Fake Nationality: Richard E. Grant (a British citizen of Dutch/Afrikaner ancestry) plays Scotsman Redferne.
- Short Runin Peru: Warlock was completed in 1988 and was set to open in May 1989, but New World Pictures went under and it took two years to find a domestic release (the film did open in 1989 outside the US).
- What Could Have Been:
- Kassandra was originally supposed to look a lot older than she does, but like William Shatner during filming of the Star Trek: The Original Series episode "The Deadly Years," Lori Singer had problems with the makeup - not for reasons of ego (Shatner didn't want to look old, even though that was kind of the point) but because the intended appliances made her claustrophobicnote , so they had to be drastically toned down.
- The infamous "breaking lady" sequence. Originally, after the channeler becomes possessed, the Warlock tears open her clothes to reveal that her nipples have transformed into a pair of eyes. Then, he stomps all over her torso, crushing and smashing it (with the appropriate sound effects), in order to free them. The scene was judged to be much too gruesome, so it was replaced with the Warlock simply plucking the channeler's eyes out instead.