Revealing mistake: Towards the end, Laurie pulls off Michael's mask, revealing his distorted face, but as he pulls the mask back down, the distorted face is also a mask as you can see the seam around his neckline.
Visible crew/equipment: When Bob gets impaled, Michael steps back to observe. Crew lights are quite visible behind Michael's head as the camera pans back. (01:05:50)
Visible crew/equipment: As Laurie heads up to the porch, the shadow of the boom is visible above the door.
Continuity mistake: When Lynda and Bob are having sex the phone rings and Bob reaches over and takes it off the hook. In the next scene when Michael comes in with the sheet on, Lynda gets out of bed and walks to the other side of the room to make a phone call.
Continuity mistake: At the beginning of the movie the only light on in the house is from Judith's room, which she turns off. Michael is seen walking through a dark house with only the hall light on. When he comes outside after killing Judith every window in the house has a light on. He didn't have time to turn them all on as he ran down the steps.
Factual error: There are palm trees visible in several scenes even though it's supposed to be set in Illinois rather than California.
Continuity mistake: After the 3 bullies are kick down Tommy with the pumpkin, they run on the right side but in the next shot one of them is running to the front.
Other mistake: In 2000 a Limited Edition of Halloween was released with 12 extra minutes of footage, filmed during the making of Halloween II in 1981. In order to air Halloween on TV they needed to remove and add certain scenes. In the original 1978 version, Dr. Loomis tells Sheriff Bracket, "I watched him for fifteen years, sitting in a room, staring at a wall, not seeing the wall, looking past the wall, looking at this night, inhumanly patient." In the Extended version, you'll see Dr. Loomis visit Michael in his room, and he's staring out of a window. Not a wall. (00:11:31 - 00:12:38)
Continuity mistake: When Laurie is talking with Tommy on the couch about the boogyman, she has her right leg on the couch but in the next shot it moves.
Continuity mistake: After Bob and Lynda have sex their bodies are closer instantly between shots.
Continuity mistake: At the Wallace house, there are windows on each side of the door. They have different designs on the inside and the outside.
Answer: There are only two families that hire babysitters in the film, the Doyle and Wallace families. Where they went is never explained, but it could be potentially anywhere. They could have gone on a trip out of town for the night, they don't have to be in Haddonfield.
BaconIsMyBFF
Where did it state this was all night? It could have been a few hours. Remember that in the next one, it is still the same night and stays night through the entire movie.