Deliberate mistake: In the first scene of the movie, we soon realize that we are looking at a house from someone's point of view who has no trouble looking over a porch railing, about 6 feet above the ground. It's revealed later that he is a little kid, about 4 feet tall. John Carpenter deliberately filmed it that way to exaggerate the impact of his little kid killer reveal. Unfortunately, when the kid is standing outside the house with his parents, you can see he could never have looked over the porch railing.
Continuity mistake: Michael is watching Annie in the kitchen. He knocks down the hanging plant in front of the door and it shatters. When Laurie goes to check on her she goes in the same door and the plant is hanging back up. (00:43:21 - 01:12:56)
Continuity mistake: The scene of Dr Loomis talking to Michael in his room, scene from the TV cut, shows him sitting in a chair his arms down at his sides. A shot of Loomis then back to Michael show his hands on his knees. Another shot of Loomis then Michael shows his left hand still on his knee but now his right arm's down at his side.
Audio problem: When Laurie's crying near the end her mouth isn't moving in sync with the audio.
Continuity mistake: More than one mask is used at the movie's end. The black material covering Michael's eyes is gone as he's trying to strangle Laurie then back as Loomis shoots him. Clearly two masks were used.
Continuity mistake: At the beginning of the film the Myers' house is within walking distance of the Strode house, both of which are on one side of town, while the Doyle and Wallace houses are on other considering the driving distance Annie and Laurie had to drive to get to them. But at the end of the film somehow the Myers' house is now within walking distance of the Doyle and Wallace houses.
Suggested correction: Annie and Laurie took so long to get to the Doyle and Wallace houses simply because they were cruising around town, giving themselves enough time to smoke Annie's weed. After they leave the hardware store when the sun was setting, they continue killing time. That's why it was completely dark by the time they arrived at their babysitting jobs; they didn't drive directly there. Remember also, Tommy walks to school too. If the Strode and Doyle houses were truly a long drive from each other, he and Laurie would've never crossed paths earlier that morning when she drops the key off. All the characters' houses in the film (and both schools) are within walking distance of each other.
Continuity mistake: When Lynda and Bob are having sex the phone rings and Bob reaches over and takes it off the hook. In the next scene when Michael comes in with the sheet on, Lynda gets out of bed and walks to the other side of the room to make a phone call.
Continuity mistake: At the beginning of the movie the only light on in the house is from Judith's room, which she turns off. Michael is seen walking through a dark house with only the hall light on. When he comes outside after killing Judith every window in the house has a light on. He didn't have time to turn them all on as he ran down the steps.
Factual error: There are palm trees visible in several scenes even though it's supposed to be set in Illinois rather than California.
Continuity mistake: After the 3 bullies are kick down Tommy with the pumpkin, they run on the right side but in the next shot one of them is running to the front.
Continuity mistake: When Laurie is talking with Tommy on the couch about the boogyman, she has her right leg on the couch but in the next shot it moves.
Continuity mistake: After Bob and Lynda have sex their bodies are closer instantly between shots.
Continuity mistake: At the Wallace house, there are windows on each side of the door. They have different designs on the inside and the outside.
