Continuity mistake: In the beginning, when the doctor is talking to the new nurse for Michael in the car, the nurse is smoking a cigarette, but seconds later she has just lit one up. If she smokes one in 45 seconds then lights up another she is one worst chain smoker I've ever seen. (00:08:05)
Continuity mistake: In the scene where Laurie comes downstairs after taking a shower, she is at her front door singing to herself and she is looking out a window directly to the left of the door. Then there is a shot of the front of her house outside and you see her exit through the door that had the window next to it, but there is no longer a window there.
Continuity mistake: When Michael is at Tommy's school, there are cars parked across the street. When he gets in the car to leave, they are gone.
Continuity mistake: Laurie's hair keeps changing throughout the movie. Her hair changes from wavy to straight while she babysits the kids. It is wavy again when she is going to Lindsey's house, and straight again when she is running back to Tommy's house. It stays straight until Michael starts to strangle her,where it becomes wavy again, having been straight in the previous shot. It all ends with straight hair. Surely all of this could not happen in a matter of hours.
Continuity mistake: When Laurie goes to leave the key, the door has two intact glass frames but when the view changes there's only one that's almost completely broken. Later when Loomis enters the house, there's two again, with one only being slightly broken. Also, the frame from the inside looks really small when Michael watches, and we don't see planks nailed across to cut out the view from inside, as well as there being a screen door that isn't there from the outside, but is there when the view is from inside. (00:13:35 - 00:36:40)
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.
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 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)
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: 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.