Continuity mistake: In the beginning of the movie, Laurie runs into Tommy while she is walking to school, meaning that they live near each other; however, later on in the movie, when Laurie has to babysit Tommy, Annie has to drive her to Tommy's house, which is located on the other side of town.
Plot hole: When Laurie and her friend see the Sheriff in front of the hardware store, he tells them someone broke in and stole "A Halloween mask, some rope, and a couple of knives." Without someone doing a complete inventory of the store, there would be no way to know the specific items that had been stolen, especially when they are such commonplace things as knives and rope in a hardware store.
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.
Continuity mistake: When Laurie is in the closet she stabs Michael with the hanger and leaves it up there. When they show all the locations at the end of the movie, in the shot of the living room look near the floor up close - you can see part of the hanger there, even though it was left upstairs.
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.
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.