Creator Backlash: Daniel Farrands was not happy with the final film, or any of it's alternate cuts, due to very heavy Executive Meddling. However, he does view the "Producer's Cut" as the one closest to his vision, and even made a big push to get it an official release.
Franchise Killer: Just barely averted. This film's savage critical reception and mediocre box office performance resulted in the next film in the Halloween franchise initially being greenlit as a direct-to-video film. It wasn't until Jamie Lee Curtis signed on and the film retooled into something of a Continuity Reboot that it became a theatrical film.
Series producer Moustapha Akkad had been intending to make a sixth Halloween film despite the tepid reception of Revenge, meeting with screenwriter and series super-fan Daniel Farrands in 1990. Farrands' ideas stoked Akkad's interest; he had compiled a notebook filled with research on the series, including a timeline, bios for every character, a "family tree" of the Myers and Strode families, and research on the runic symbol of Thorn that had appeared in Revenge. His intent was to bridge the first two films with the fourth and fifthnote For those wondering where the third film fits in: that film, Season of the Witch, was a non-canon spinoff that featured none of the series' characters and was subsequently ignored, viewed as something of a Black Sheep in the series today., and also to explain why series villain Michael Myers keeps coming back: he had been put under an ancient Celtic curse that compelled him to murder his entire family, one that would be passed on to another young child after he completed his task.
Farrands was brought on to write the film, but a series of complicated legal battles held up production for years until Miramax Films (via Dimension Films) bought the rights to Halloween. Writing finally began in 1994; several screenplays by different writers were gone through and deemed insufficient until Farrands' final draft, dubbed Halloween 666, was finalized after eleven drafts. From there came casting; while Donald Pleasence reprised his role as Dr. Loomis, Danielle Harris did not return as Jamie Lloyd, due to both salary disagreements and Creative Differences. The producers wanted to recast Jamie with an adult actress anyway, but Danielle attempted to keep the part by getting herself legally emancipated. She walked away from the project when the writers reduced her character, and she was only offered scale. Fred Walton was also tapped to direct, but dropped out and was replaced with Joe Chappelle shortly before production.
Then production began, and the real problems hit. Shooting in Salt Lake City proved challenging due to an early winter that frequently interrupted production, and Chappelle and producer Paul Freeman had to rewrite the ending on the fly to meet deadlines. Furthermore, Freeman frequently inserted himself into production, rewriting dialogue and action scenes, removing a number of scenes from the script, taking it upon himself to direct second-unit shots, and sending the crew home when important scenes needed to be shot. Freeman's handling of the production was so inept that Miramax eventually stepped in, kicked him off the film, and ordered reshoots.
Post-production went no better. Lead actress Marianne Hagan described the test screenings in early 1995 as "consist[ing] primarily of 14-year-old boys" who disliked the ending and the Cult of Thorn storyline. This led to another round of reshoots to craft a new ending, but there was a big problem: Donald Pleasence could not be present for them on account of having died in February. Not only was a new ending shot anyway, but over twenty minutes of other footage was changed as well, leaving gaping plot holes that rendered the film nearly incomprehensible.
When it was released that September, Curse had the largest opening weekend out of the entire series but was ravaged by critics and fans, and plunged fast. One of its fiercest critics was Farrands, who hated the final film's deviations from his script. The series would be partially rebooted three years later in 1998 with Halloween H20: Twenty Years Later, which took only the first two films as canon. Eventually, when the film was shown on TV, someone unearthed the original Producer's Cut from before the reshoots; while it cuts the violence and profanity for TV airing, it otherwise retains most of the original content, and Farrands has given it his tepid (if still disappointed) approval. The full Producer's Cut was finally released on home video (after having been a popular bootleg for years) in 2014 as part of the collector's edition box set of the entire series.
What Could Have Been: Before the "Cult of Thorn" plot was fleshed out, the writers toyed with the idea of having the Man in Black be revealed to be Michael's father.
Donald Pleasence died during the shooting, so we never got to see his personal confrontation with Michael.
Not exactly true. The Producer's Cut of Halloween 6 was a finished version of the movie and the version producer Moustapha Akkad wanted to release (hence the name). Donald Pleasence successfully finished shooting of that film. It was only when the reshoots came about for what would become the Theatrical Cut that Pleasence had died.
Danielle Harris wanted to reprise her role as Jamie, and even had herself emancipated so she could work on it, but was turned down when the character's appearance was reduced, and she refused to work for scale.
Brian Andrews, who played the original Tommy Doyle in the first Halloween was considered for the role. However he didn't have an agent at the time and so couldn't be contacted. He later said he regretted it for years.
Denise Richards apparently auditioned for the role of Beth. Likewise the part of Dr Terence Wynn was written with Christopher Lee in mind.
As mentioned above, the original ending (seen in the Producer's Cut) has the Thorn curse passing to Loomis, with Michael, now presumably freed from his compulsion to kill, disappearing to parts unknown. Had the following sequels actually ran with this idea, the franchise's status quo could have been drastically altered.