Revealing mistake: Lynda calls Laurie using a rotary phone yet doesn't even look at what she's dialing. And you can tell she's not actually dialing in the first place.
Continuity mistake: At the start of the film Michael smashes the window, later on at the school the window is intact.
Continuity mistake: Michael breaks the passenger front door window on the wagon when he takes car, a short time later when he's driving in town the window is not broken.
Audio problem: While Lynda is filing her nails just as Michael enters the scene wearing a sheet and glasses, the sound of her filing continues despite her pausing.
Visible crew/equipment: As Laurie heads up to the porch, the shadow of the boom is visible above the door.
Continuity mistake: Before Tommy breaks the pumpkin at the school in the background there are 2 kids, one with a hat holding something in his hands which disappears in the next shot.
Continuity mistake: After Laurie gets home and her room she leaves her bag and some books on the bed - they change position between shots.
Continuity mistake: When Bob and Lynda get to Annie's house he leaves the door of the truck open, but when Laurie is on the street the door is now closed.
Revealing mistake: When Michael cuts Annie's throat, notice there's no visible cut or blood at all. When your throat is cut blood is going to pour out.
Suggested correction: True, but the view we have is distorted because it's shown through the windshield in a dark garage. Blood most likely poured out, but we don't see it because of how it's shown to us.
In the documentary, John Carpenter specifically stated that he left out of the gore on purpose. He wanted to film the movie so that the viewer would have a "mental image" of the kills without all the blood. He wanted it to be left to the imagination of the viewer.
Continuity mistake: Michael stabs his sister repeatedly. The amount of blood shown on the knife when his parents come home is nowhere near enough for the number of times he stabbed her. (00:06:35)
Factual error: In the scene when Laurie gets stabbed by Michael in the arm she falls over the banister - the camera shows a view of what she sees, falling at that angle Laurie would have broken her neck, spine and hip. But it is still weird how she managed to turn 180 degrees in such a short fall. (01:16:40)
Continuity mistake: In the beginning of the film when Michael is walking through the house, the clocks have different times on them. After he walks by the clock in the living room, it says 9:40. Seconds later, it strikes ten times.
Suggested correction: This scene jumps ahead as Michael was in the living room waiting for them to finish having sex and the boyfriend to leave.
Continuity mistake: When young Michael Myers sees the clown mask, Judith's clothing is bunched up together on the floor. When he puts the mask on, Judith's sweater is lying separately from the rest. (00:05:15)
Plot hole: Since the station wagon from the asylum was stolen, it should have been reported stolen along with the escape of Mike Myers. So why was the sheriff department not looking out for the stolen station wagon? We see Myers driving that station wagon freely without being stopped, while wearing a mask in broad daylight.
Character mistake: When Laurie and Annie are on their way to babysit, and they see Annie's dad, the cop, as soon as they pull up to say hi and roll the window down, he mixes the two names up, and calls Laurie Annie, and Annie Laurie. You'd think he knows his own daughter's name. (00:32:10)
Continuity mistake: When Laurie, Annie and Lynda are walking home from school, the part where Lynda walks to her house you can see the station wagon on the side of the road behind them. A few seconds later it has moved up the side of the street.
Other mistake: In 2000 a Limited Edition of Halloween was released with 12 extra minutes of footage, filmed during the making of Halloween II in 1981. In order to air Halloween on TV they needed to remove and add certain scenes. In the original 1978 version, Dr. Loomis tells Sheriff Bracket, "I watched him for fifteen years, sitting in a room, staring at a wall, not seeing the wall, looking past the wall, looking at this night, inhumanly patient." In the Extended version, you'll see Dr. Loomis visit Michael in his room, and he's staring out of a window. Not a wall. (00:11:31 - 00:12:38)
Continuity mistake: After Michael hides behind a hedge bush and Laurie and her friend go to investigate, the sun changes between shots.
Continuity mistake: When Laurie stabs/pokes Michael with the clothes hanger while in the closet, you can see that she brings the hanger back down, but when it cuts to Michael, it's still stuck in his eye.
Revealing mistake: When Tommy is trying to show Laurie that Michael is outside, something to the left of the Wallace house looks like legs moving around in the dark and then jumping up. Presumably, this is Nancy Kynes jumping up into Tony Moran's arms so that he can carry her around the front of the house, which is actually the shot that is used about ten minutes later. Carpenter potentially used this shot of the house either unaware that they could be seen, or didn't anticipate the future change in aspect ratio. (00:45:30 - 00:55:30)
