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.sam norton
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). (00:24:10)
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. (01:19:50)
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.