Rachel dumps coffee on Kelly's white t-shirt, but it doesn't stain or even get wet.
(at around 14 mins) Michael's full name is Michael Audrey Myers yet in the mental hospital when someone is typing his name on a form they write Myers, Michael M (possibly character error).
(at around 18 mins) When Dr. Loomis parks his car outside of the filling station, he stops past the last gas pump. The next shot shows his car much closer and he tries to fill it up.
The burn scars on Dr. Loomis' face change periodically throughout the movie. There is a dramatic change from when he is riding in the truck with the preacher on his way to Haddonfield compared to when he arrives and comes into the police station.
In the scene at the school when Michael attacks Dr. Loomis, the hair on the mask he is wearing is light gray/white as opposed to the normal dark hair.
Michael hides in the back of Deputy Logan's patrol car when the deputy drives from the Carruthers house to the Meeker house, and slips out unbeknownst to anyone after the deputy arrives. In reality, back doors on patrol cars could not be opened from the inside because this would allow a prisoner to escape from custody.
There is no reason for Michael's head and face to still be bandaged after 10 years.
The patrol cars and uniforms read "Haddonfield Police Department", and several (not all) characters refer to the "police station", yet Meeker is a sheriff, not a police chief, and all of his men are deputies, not officers. As such all of the livery should read "(Warren) County Sheriff's Department", as a sheriff's department and police department are two different, separate law enforcement agencies. Everything in the previous films was correctly referenced.
(at around 14 mins) When Jamie and Rachel first discuss going for ice cream, Jamie asks, "Double scoops?" and Rachel agrees. (at around 24 mins) After school, in the car, Rachel asks Jamie whether she wants to go to the discount store or Dairy Queen. Dairy Queen serves soft-serve ice cream, which cannot be scooped. At the time of the film, Dairy Queen did briefly test market "hard ice cream" which could be scooped, but it didn't last long.
When Sheriff Meeker confronts the kids dressed as Michael, he says, "If I catch you again, it's a weekend in jail," which indicates it is a Friday. Halloween fell on a Monday in 1988.
Michael got his overalls from a mechanic he killed by impaling the guy with a metal rod in the chest area. Yet there is no blood or holes on the coveralls.
(at around 1h 10 mins) When Rachel is on the roof of the house and fighting Michael, she slides down the roof and slams into the chimney. When she does, the "brick" chimney flexes as though it's made out of thin wood.
How was the police officer able to back out of his driveway let alone get into his car without seeing Michael, who is portrayed as a pretty tall man laying across his backseat? If you look closely, you can even see him turn his head and adjust his body in order to back out of the driveway so how was he not able to see Michael in his backseat?
(at around 6 mins) When Michael is in the ambulance car after he grabs the guy on the head he sticks his thumb in his forehead, and on the left you can see the end of the fake arm.
(at around 45 mins) After the power goes out, Jamie is on the sidewalk and hears Rachel calling for her. In the background, you can see tulips getting ready to bloom. Filming was obviously done in the spring rather than the fall.
In every scene before Myers is shot at or struck, it is obvious that there is protective padding under his coveralls.
(at around 1h 25 mins) Leslie L. Rohland's character of "Lindsey" is listed as "Leslie" in the end credits.
Michael Myers had been at Smith's Grove - Warren County Sanitarium prior to his escape in Halloween and was being transferred to that location at the beginning of this movie. The patches on the medical personnel say Smith's Grove, but the ambulance is labeled as Smith Grove.
In the scene where Brady loads the shotgun as Michael ascends the stairs, when Brady looks up, the front door can be seen directly behind Michael, which shouldn't be possible, as they are on the stairs in the middle of the house.
As Deputy Logan leaves the Carruthers house to go to Sheriff Meeker's house, he and Meeker are communicating by radio, and he advises Meeker that he just heard about the other deputies being killed at the police station. Since Meeker and Dr. Loomis were seemingly the only characters who knew about this, how could he have found out about his colleagues being killed?
When Deputy Logan leaves the Carruthers house, Mr. and Mrs. Carruthers pull up to their driveway literally seconds after he leaves in his patrol car. It seems odd that they wouldn't have noticed this, or that they wouldn't have taken more initiative to find out why he was at their house, especially since Rachel and Jamie weren't at home during a power outage.
(at around 1h 1 min) When Rachel throws the cup of coffee at Kelly, we hear Rachel say "Have some coffee!" but her mouth clearly says something different.
(at around 15 mins) When Dr. Loomis & Dr. Hoffman are in the mental hospital, Dr. Hoffman answers the phone. He says, "I see. I see, thank you," but his mouth movements don't match the words. We then hear him yell, "Loomis! Loomis!" but he is clearly not actually yelling.
When Jaime is trying to escape from Michael when he grabs her by the foot, she tries to escape by grabbing the carpet and there are a lot of claw marks on the carpet, but in the next shot, some of the visual claw marks disappear.
(1:20:32 minutes into the movie) The sound says, "Die you son of a bitch!" But the words that come out of her mouth were, "Die, son of a bitch," without saying the word, "you."
(at around 47 mins) When Jamie and Rachel get into the cop car and Sheriff Meeker drives off, you see Michael Myers standing in the road. Right before the scene ends, crew making the smoke blow are visible on the far left of the screen.
(at around 21 mins) The cameraman is reflected in the window when Dr. Loomis runs to the window to look for Michael.
(at around 33 mins) A camera is reflected in the window when Rachel is getting up to go get Jaime.
(at around 33 mins) When Rachel is waiting for Jamie to go trick or treating, right as she gets up from the couch, the camera is reflected in the window.
(at around 23 mins) Reflected on the side of Lindsay's car as Jamie is getting into it.
When Loomis enters the Sheriff's Office and asks to speak to Sheriff Brackett, the deputy tells him that Brackett retired and moved to St. Petersburg, Florida, and that Loomis will have to travel 3,000 miles south to see him. Haddonfield is located in Illinois. No matter what part of the state it is in, it would not be anywhere near 3,000 miles away from St. Petersburg.
The movie takes place in Illinois, but the telephone at the insane asylum has an area code of 317, which is neighboring Indiana. In mitigation, Michael was described as a federal prisoner and could possibly have been transported across state lines.
At around 11 minutes, behind the houses and the school bus in Haddonfield, Illinois (as indicated on the screen) mountains are clearly visible through the trees. As we all know there are no mountains in Illinois.
(at around 49 mins) Deputy Logan, who was left at the Carruthers' house to wait for the family to get back home, runs out of the house to his patrol car. He gets on the CB and tries to get in touch with the sheriff on the radio. After getting a response, he says he "just heard about the station", at which point, the sheriff tells him to head over to his place. This was after Michael threw "Bucky", the electrical worker, into the electrical wires and put the whole town in the dark. Logan couldn't have heard about what happened from inside the house, as he had to run to the car to get to his radio.
The entire point of the rooftop scene is that the characters are trapped in the house and cannot escape. However, when Rachel and Jamie fall off the roof, Michael somehow gets down from the roof to the front yard in a matter of less than a minute. He should have had no alternative than to go off the roof as well, but it is clearly implied that he just went back in the house and walked downstairs.
(44 minutes into the movie) When Rachel is looking for Jaime and sees Michael Myers, Michael seems to be ahead of her. But when Rachel sees him, she seems to be running toward him and not the opposite direction that Michael is in. Why would anyone want to be running in the direction that a killer is in?
When the security guard explains to the hospital staff what happened in 1978, he references Dr. Loomis shooting Michael Myers 6 times, then setting him on fire - Clearly referencing events from both Halloween (1978) and Halloween II (1981). However, Dr. Loomis shot Myers a total of 11 times (6 in the Wallace house, and 5 in the Haddonfield Memorial Hospital Emergency Room entrance) and then set him ablaze by causing a gas explosion.
In the ambulance, once of the workers said that Michael is a state ward because Jamie is too young to be his ward. He meant Jamie is too young for Michael to be her ward.