On the television in the girls' room a clip from Scream 2 (1997) is showing, reciprocating numerous Halloween (1978) references and clips in Scream (1996). However, according to producer Moustapha Akkad when the scene was filmed, the girls were actually watching So I Married an Axe Murderer (1993), making an entirely different joke: a movie featuring Michael Myers had its characters watching Mike Myers. The clip was changed to Scream 2 (1997) in post-production.
The reports that Kevin Williamson's original treatment for "H20" included a scene in which "Halloween 4" through "6" are acknowledged as being "in continuity" and "canon" are completely accurate. The scene did exist, and involved a bitchy student at Keri/Laurie's school giving a class report on the "Haddonfield Murders", and going into great detail about Jamie Lloyd, Danielle Harris and JC Brandy's character from "Halloween 4" through "6". The student talks about Jamie losing her parents in an auto accident, as was the explanation in those sequels for Laurie Strode's absence. (In fact, the only reason for Laurie to be in the Witness Protection Program with her son under an assumed name as "Keri Tate" at all was because the original story for "H20" was conceived like this, with "Halloween 4" through "6" in continuity, and Williamson thus being required to create an explanation for Laurie's "death" in the previous movies and her subsequent resurrection.) The student's report chronicles Jamie's being hunted and eventually killed by her uncle, Michael Myers. Upon hearing this oral presentation in the classroom, a grief-stricken Keri/Laurie then retreats to a restroom and throws up. This scene was of course omitted from the actual film.
During the scene where Norma is leaving, she stands in front the car from Psycho (1960). The music playing in the background at this part is also from Psycho. Janet Leigh, who plays Norma, played Marion in Psycho. The license plate on the car is also the same as the second car Marion buys in Psycho, NFB 418, which are Norman Bates' initials.
P.J. Soles was originally approached for the role of Keri Tate's/Laurie Strode's secretary. Soles never gave a straight answer as to what she wanted to do, skeptical about returning to the series as someone completely different then her character Lynda, originally killed off in Halloween. She eventually lost the role to Jamie Lee Curtis's mother, Janet Leigh, who was approached after not getting an answer from Soles.
When Jamie Lee Curtis' character says, "go down the street to the Beckers..." this was supposed to refer to the line from Halloween (1978) , "go down the street to the McKenzie's house..." The name was changed to Becker, which was the last name of Drew Barrymore's character in Scream (1996).
Contrary to popular belief, Kevin Williamson was in fact not the original writer of the film. Originally, Robert Zappia was hired to pen 'Halloween 7,' which was planned to go direct-to-video after the modest box office performance of Halloween: The Curse of Michael Myers. Zappia's original script was set in a fenced-in boarding school as does the finished film. However, when Jamie Lee Curtis expressed interest in returning to the series, Kevin Williamson--who was coming off of his blockbuster success with Scream--was asked by Dimension Films to pen a treatment that added Laurie Strode. When the WGA deemed that Williamson did not deserve writing credit on the screenplay, Dimension Films--hoping to market the film as 'From the creator of Scream'--offered Zappia more money to share the writing credit. Zappia declined, and Williamson only possesses Executive Producer credit on the finished film.
Due to its shoestring budget, the prop department of the 1978 original had to use the cheapest mask that they could find in the costume store: a Star Trek William Shatner mask. They later spray-painted the face white, teased out the hair, and reshaped the eye holes. Shatner admitted that for years he had no idea his likeness was used for this film. It was only during an interview that someone mentioned his mask was being used. He has since stated that he is honored by this gesture.
In certain scenes, Michael can be seen wearing two different masks. The director decided well into production, to go with a different mask, so certain scenes were re-shot. Some scenes with the original mask can still be seen, and in one shot it had to be altered with CGI to replace Michael's old mask with the new one.
During the credits in the prologue, Dr. Samuel J. Loomis' dialog from the first film about Michael's incarceration is heard. The studio, instead of recovering the original audio from the original scene, decided to use a sound-alike actor named Tom Kane to provide the voice-over.
According to H6 writer Daniel Farrands, who wrote an early draft of the film, said there was originally a scene scripted and supposedly filmed where a student in Laurie's class does a report on a book called "The Halloween Murders", in an effort to tie all the movies together. This was dropped however, when it was decided by the director and producers to ignore "H3-6" so as to concentrate more on the Laurie Strode aspect of the story.
Kevin Williamson was originally hired to write the script and was said to have actually finished a draft or two with the input of Jamie Lee Curtis. Williamson's script was eventually not used, but a treatment he wrote for the movie is said to be a heavy basis for the final, filmed version.
The original treatment for "H20" by Kevin Williamson was much more sparse on character detail and had a radically different ending. In the place of Nancy Stephens' character of Marion Whittington in the trademark "Williamson opener", a new character was originally to be created, "Rachel Loomis", apparently Dr. Sam Loomis' daughter, who would have the computer files on Laurie Strode/Keri Tate on her home computer. Rachel would come home to discover her computer on, and would swiftly be dispatched by the Shape. Also, in the climax of the treatment, there is a massive helicopter and bus chase sequence, culminating in the downed helicopter spinning out of control and decapitating the Shape with its out of control rotor a la "Mission: Impossible".
The newspaper clippings in the beginning were meant to be the only link to Halloween's 4-6 after the scene in the classroom was cut, and would have included clues such as "Mysterious cult kept murders hushed up in Haddonfield" and "Jaime Lloyd missing" with dates such as 1995 and 1989, in the end only one "headline clue" was left in, a pair of bloody scissors that may have been the one's used to kill Rachel Lloyd in the fifth film.
The majority of John Ottman's original score was rejected late in post-production and replaced with Marco Beltrami's scores to Scream (1996), Scream 2 (1997), and Mimic (1997). The producers wanted a darker, more Scream-like score, while Ottman's score wasn't strong enough to fit the bill. Some of what remained of Ottman's score was heavily edited and often was used for scenes for which they were not originally intended. Nonetheless, Ottman's music was later released in its entirety on an album entitled "Portrait of Terror", from Varese Sarabande Records.
On one of the newspaper clippings seen during the opening credits, a picture of Dr. Sam Loomis can be seen. The character was featured in the previous Halloween films, and was portrayed by Donald Pleasence.
The trivia items below may give away important plot points.
Moustapha Akkad (the executive producer) said that the killer in H20 was not actually Michael Myers, but in fact a copycat killer, and that this would be explained in the next Halloween movie. The idea was dropped for Halloween: Resurrection (2002), which explained the reappearance of Michael Myers by revealing that he had traded places with a paramedic at the end of H20, who had then been mistaken for Michael, and was subsequently beheaded by Laurie.
One of the biggest sources of tension between the filmmakers was the issue of the film's ending. Kevin Williamson's treatment had the Shape being cut in half by a helicopter rotor while early drafts of the script had Laurie stabbing him through the heart with a javelin while he was pinned between the two pieces of a retractable gym floor. Moustapha Akkad wanted the Shape to live at the end so he could produce more Halloween films while Bob Weinstein at Dimension Films wanted the Shape to die. Weinstein instructed screenwriter Robert Zappia to write two endings and send the ending with the Shape surviving to Akkad while they would actually shoot the ending where the Shape died. Zappia refused, much to Weinstein's annoyance. According to Zappia, Kevin Williamson concocted the film's ending where the Shape is "killed," as well as the twist shown in Halloween: Resurrection (spoiler) where it is revealed that the Shape had switched clothes with a paramedic. This solution managed to appease both parties. According to screenwriter Matt Greenberg, it was Weinstein who suggested that Laurie Strode decapitate the Shape with an ax.
There was at one time a plan for Michael Myers to speak a single line at the end of the movie. He was to have said "Laurie" just before being beheaded by Jamie Lee Curtis. This idea was dropped from the final script.
The original versions of the script differed greatly from the finished film with the character Ronnie written as a woman named Hattie (who was killed) and the character Molly also getting killed by Michael Myers.