Jamie Lee Curtis agreed to do her part, only to make sure her character, Laurie Strode (or herself) wouldn't appear in another sequel. (At the time of the film's initial release, executive producers Malek Akkad, and Moustapha Akkad tried to explain it by claiming Jamie Lee Curtis "was so impressed with the screenplay, that she wanted a large part in it". She has publicly stated that was not the case, she was under contract to do it.)
Several new endings were written during production and the cast was never sure how the film was actually going to end. Four different endings were filmed, and the director wanted the studio to ship a different ending to each theater, a technique used before during the theatrical release of Clue (1985). However, the studio disagreed and the endings now appear on the DVD and the Internet.
Originally, the executives of Miramax wanted to continue the series by creating a whole new story of which didn't have anything to do with Michael Myers after the last film, in a similar manner to Halloween III: Season of the Witch (1982). However, poll results conducted throughout fan websites proved to the producers that fans wanted Michael Myers to return again.
This is the second Halloween film to make any sort of reference as to what exactly Michael Myers eats. In the original Halloween (1978), when Sheriff Brackett and Dr. Loomis enter the Myers house, they see something on the floor, which turns out to be the corpse of a dog. Dr. Loomis simply says "He got hungry."
Michael Myers is not given credit for any of the murders that occur in Halloweens' 4, 5, or 6. A sanitarium resident even notes that Myers was not heard from for the twenty years between the events that occur in Halloween II (1981) and Halloween H20: 20 Years Later (1998).
Actor Kyle Labine, who appears as a party goer in this film, also starred as Bill Freeburg in Freddy vs. Jason (2003). This makes him the first person to appear in a Michael, a Jason and a Freddy film.
At the start of the film, an asylum inmate recounts how Michael Myers had stayed out of sight for "these three years", i.e. since Halloween H20: 20 Years Later (1998). This places the events of that scene in 2001 - the first year to have a full moon occur on Halloween since 1945.
The name of the psychology professor at Haddenfield University is Dr. Mixter. This was also the name of the doctor in Halloween II (1981) that treated Laurie Strode (Jamie Lee Curtis) and was killed by Michael Myers with a needle in the eye.
Halloween: Resurrection concludes with the potential for another sequel to continue the story, Josh Hartnett was originally planned to reprise his role as John Tate and seek revenge for his mother's death.
(at around 2 mins) In the first scene at the college, Sara Moyer (Bianca Kajlich) is shown twirling her hair, much like Laurie Strode (Jamie Lee Curtis) does in the class room scene in the original Halloween.
(at around 16 mins) At the beginning of the movie Harold begins to recount the victims of the first two films and he says 3 teenagers were killed, along with 3 nurses and a paramedic. This is completely wrong. 4 teenagers were killed (Annie, Bob, Linda, and Alice) and 4 nurses, a paramedic, a security guard, a doctor, and the officer with Dr. Loomis. Also the truck driver who was found by Dr. Loomis, which is where Michael got his clothes.
The name Jen Danzig is a reference to Glenn Danzig, the former singer and leader of The Misfits, who wrote and sung the songs Halloween and Halloween II after the original movie was released. The two songs have nothing to do with the movies, because their lyrics do not even touch the main plot.
Jamie Lee Curtis was contractually obligated for a 30-second cameo in the film, but reportedly was so interested in the story that she agreed to do a full four-day shoot and appeared in the entire opening sequence.
With Laurie's death in this film the only two recurring lead characters in a horror franchise to not have been killed by the series killer are Kristy Cotton from Hellraiser (who survived four battles with the demon Pinhead) and Sidney Prescott from Scream (who survives 4 battles with Ghostface).
Michael switching outfits with the paramedic (how he survived the previous film) is similar to the producers' cut ending to Halloween: The Curse of Michael Myers (1995), where Michael switches outfits with Dr. Wynn.