Continuity mistake: The Myers' house is close enough to be walking distance from where Laurie lives. Yet at the end of the movie when Loomis notices the station wagon right down from the Myers' house, Loomis himself is a mere walking distance from the houses at which Laurie and Annie were babysitting. This is impossible since we were already told the street where the babysitting was taking place at was on other side of town from where Laurie lived.
Continuity mistake: When the girls are walking home from school, Annie says that she is babysitting Lindsey Wallace and Laurie says she is babysitting Tommy Doyle. Laurie also claims that the Wallace's and the Doyle's house are 3 doors down, but when Annie drops Laurie off the houses are right across the street from each other.
Continuity mistake: After Laurie asks Annie what she is going to wear to the dance (while Annie is driving with Laurie), we see Annie turn the steering wheel to the left, yet the car turns right as seen on the green screen in front of them. As the car is turning right, it cuts back to Annie still turning the steering wheel left. (00:33:45)