Plot hole: Early on, the TV in the Elrods' house is showing a report (corroborated by the authorities) of three bodies being found in the Wallace house. However, later on during the Ben Tramer accident scene, the deputy rushes up to the sheriff to inform him that three bodies were found (including his daughter Annie).
Character mistake: When Ben Tramer's friends report him missing to the police, they describe him as being 17 wearing a mask. This is what leads Loomis to make a positive ID... on Halloween.
Character mistake: The coroner determines that the burnt body of Ben Tramer (still unidentified) must be young, based solely on the absence of fillings in his teeth. Nobody considers for a moment that it could be a 30-something with good dental hygiene.
Continuity mistake: The front door on the Doyles' house is different from the one seen in Halloween. You can see this when Dr. Loomis leaves the house in the beginning of the movie.
Visible crew/equipment: At the hospital cafeteria, Jimmy and Bud are on a break when Nurse Karen comes in and briefly speaks with them. As she leaves you can see the reflection of the boom microphone reflected in door glass when it closes. Just before Bud starts singing. (00:28:33)
Visible crew/equipment: When Dr Loomis, Marion and the marshal arrive at the hospital, Loomis tells the marshal that he thinks he'll "need him in there" and you can see the camera reflected in the marshal's rear view mirror. (01:14:28)
Continuity mistake: When Jimmy finds Nurse Alves dead on a stretcher and slips over in her blood pool, he hits the floor and there is a lot of blood on his face (especially near his mouth). A second later however, in an overhead shot, his face is clean. (01:03:25)
Continuity mistake: After Laurie wanders into a hospital room and unsuccessfully tries to use the telephone there are a series of shots cutting back and forth between the room and Laurie looking out into the hallway. In the shots from inside the room the telephone shifts position at one point. (00:59:01)
Continuity mistake: When Michael is stalking the hospital corridors there is a scene when he hides in the baby unit and is observing the Head Nurse berate Nurse Karen for being late again. The scene switches back and forth between a close up of the two nurses talking to a shot from Michael's perspective of them from inside the baby unit. In the close up the Head Nurse's body is facing Karen, from Michael's perspective her body is facing towards him on the other side of the nurse station. (00:30:20)
Visible crew/equipment: When the kid with the boom box on his shoulder walks into Michael you can see the cameras shadow pass over Michael as it pulls back to reveal him. (00:24:42)
Visible crew/equipment: When the two paramedics are putting Laurie into the ambulance you can see the shadow of the camera cast on the stretcher as it passes across the driveway. (00:12:40)
Other mistake: Jimmy the paramedic walks into the major surgery room to find Ms. Alves dead on the stretcher, the blood drained from her body. As he turns to leave he suddenly 'slips' on the pool of blood, falling back first and knocking himself unconscious. However the next shot reveals that the blood pool extends out to the doorway, so there's no way he could have crossed to the stretcher without slipping in the first place while entering the room.
Continuity mistake: After the guy in the hospital slips in the blood puddle he has some blood on his face and mouth that disappear between shots.
Continuity mistake: After Loomis and the police officer see the fake Myers they leave the car with the doors closed but in the open view they are open again.
Continuity mistake: After the hospital guard takes a look outside he checks the trash container which has inside a box with a big bloodstain which disappears in the next shot.
Continuity mistake: When the guard is checking the warehouse at the hospital he holds the flashlight differently between shots.
Other mistake: After Myers stabs the blonde nurse the scalpel is clean of blood.
Audio problem: When Loomis shoots Michael in the opening here his gun sounds different from the previous movie.
Continuity mistake: When Michael's shown falling off the Wallace balcony in the opening scene it's on the front of the house not the back. Clearly this is a different house. (00:02:31)
Other mistake: When Michael dips the nurse's head into the scalding water, her face starts to burn and her skin starts to peel. But, nothing happens to his hand that is also going in the water while holding her hair. (00:52:15)
Answer: There is a scene where Laurie dreams about meeting Michael as a young teen. It's unknown whether this is an actual memory of real events, but since nothing indicates otherwise, we could assume the he saw her at an older age when she looked closer to her 17-year-old self.