Continuity mistake: In the scene when Michael is carrying Annie's body into the house her head is on the left side of his body. After they show Tommy looking out the window they cut back to Michael and suddenly Annie's head is on the right side of his body.
Revealing mistake: Even though the story is set in Haddonfield IL, all of the cars have California license plates.
Visible crew/equipment: There is a scene where Michael Myers is hiding behind a hedge bush and Laurie and her friend go to investigate. Laurie turns around and talks and you see cigarette smoke go by the camera (John Carpenter admitted on the commentary track that he was smoking a little too close to the camera that day).
Visible crew/equipment: Just before Laurie stabs Michael with the knitting needle you can see that one of the window shutters is open and that the wind is ruffling the curtain. When the camera gets closer and the curtain is out of the way you can see the huge fan in the studio being used to simulate the wind outside.
Continuity mistake: In the closing credits, Michael Myers is said to be 23 years of age, he was actually 21.
Continuity mistake: When Laurie is beating on the door to Tommy's house and telling him to open it, the door knob is on the right side of the door. When it shows Tommy opening it from the inside, the door knob is also on the right side (it should be on the left).
Plot hole: We see Michael wearing the mask throughout the day, from morning at the Myers House, to mid-day outside Laurie's school, to afternoon when Tommy is leaving school, yet when Laurie and Annie see the sheriff in front of the hardware store on the way to their babysitting jobs (presumably in late afternoon or early evening), the store's alarm is still ringing and the sheriff mentions that one of the items stolen was a Halloween mask.
Factual error: When Dr. Loomis is at the pay phone talking to someone at the mental institution, the background of the scene has mountains, which in fact Illinois has hardly any mountains, and the few it does have are nowhere near there.
Continuity mistake: When Laurie is waiting for Annie to pick her up, she is waiting with a pumpkin and it's still very light out. But when they arrive at the houses where they babysit, which wouldn't take ages to travel to, it's dark outside.
Continuity mistake: There is a scene involving Michael Myers breaking the closet in order to get to Laurie, then why near the end of the film does it show you the closet in tip-top condition?
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.
Continuity mistake: When Annie and Laurie leave the hardware store to go to their babysitting jobs it is broad daylight. When they reach the houses apparently just a few blocks away, it is already dark.
Plot hole: Immediately after the scene where Laurie is talking to Linda while she is being strangled by Michael, Laurie looks out the window and sees the LOWER level of the other house lights turned on. Michael was on the upper level and could not have gotten down the stairs to the first level in time (1 or 2 seconds) to have turn on the lights.
Continuity mistake: In the scene where Laurie walks across the street to check on her friends, the porch of the Doyle house has nothing on it. When Laurie runs back across the street and starts pounding on the door she picks up a flower pot off the porch to throw at the window.
Continuity mistake: The date on the tombstone above Annie says that Judith Myers was born November 10, 1947, and died October 31, 1963. that would make her 15 (not quite 16 yet) at the time of death, yet everyone says that she was 17 years old.
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.
Visible crew/equipment: When Annie is locked in the laundry room, there's a scene where the phone is ringing incessantly and the camera pans slowly to the right showing little Lindsay Wallace who's too busy watching television to answer the phone. If you watch this scene in widescreen, you'll see a crew member lurking in the shadows (left side of the screen) on the wall. It appears they are trying to avoid being seen.