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: 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: 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.
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.
