- Perhaps surprisingly, one of the most difficult scenes to shoot was that of Dr. Challis tossing the skull mask on the security camera as it kept landing right away. It took over forty takes to finally achieve the version seen in the film.
- Don Post Studios was contacted to make the molds and mass market the masks used in the film. The company agreed quickly, after initially turning down the opportunity for Halloween.
- Nigel Kneale wrote the original draft for the film, which was later rewritten by John Carpenter before Tommy Lee Wallace did a further rewrite. Nigel Kneale refused to be credited, so Tommy Lee Wallace received sole screenwriting credit, despite claims that ~60% of the final draft was the work of Nigel Kneale.
- Tom Atkins stated during press for the film that a few different endings were shot, and he had no idea which would be used. Unfortunately, none of those alternate endings have ever surfaced.
- Due to time restraints on the film’s turn around, Stacy Nelkin was cast on the spot in her audition. She and Tom Atkins didn’t have time to properly get to know each other before having to shoot their love scene as their first scene together.
- Stacy Nelkin had never seen the first two Halloweens before she auditioned for Season of the Witch. After receiving the role, she went back and watched them.
- Though largely rumoured to have been the voice of the Santa Mira announcer, Tommy Lee Wallace, Sean Clarke and Jamie Lee Curtis have all individually confirmed that Jamie Lee Curtis had no involvement in this film.
- After killing off Michael Myers at the end of Halloween II, the concept behind the Halloween franchise going forward was to make a new film each year centred around the holiday of Halloween, but each film being its own stand-alone story.
- London Bridge is Falling Down was selected as the base theme to use for the Silver Shamrock Jingle as the song is public domain.
- All of the names on the hotel’s sign-in list are the names of members on the crew.
- Santa Mira was the name of the city in Invasion of the Body Snatchers, which is why it was chosen as the setting for this film.
- With a timeline from Saturday, October 23 to Sunday, October 31, Season of the Witch actively portrays the most amount of days of any Halloween film next to Rob Zombie’s Halloween remake, which portrays an undetermined amount of days in Michael’s youth.
- While the film ends with ambiguity over whether or not Dr. Challis was successful, the novelization by Dennis Etchison reveals that he ultimately failed.