Continuity mistake: At the end of part one, Laurie's stab wound was just a streak of blood and none on her shirt at all. When they bring her out to the ambulance, there's now a lot of blood on her shirt and streaks of blood on her arm. (00:13:20)
Continuity mistake: After getting out of the car, Laurie is on the ground beside Jimmy's car outside the hospital when she sees the Marshall's car pull up. When Loomis tells the Marshall he ought to handcuff him to the wheel, if you look, Jimmy's car is still visible in the distance, but Laurie is not in that shot.
Continuity mistake: In the scene where the boys ask Mr. Hunt about Ben Tramer, Mr. Hunt says that "it's just a little past 11." Following this up in the next scene Bud lures Karen into the room to kiss her and wish her Happy Halloween. During this scene, as Bud reaches up to kiss Karen, his watch is clearly visible and shows the time as 1:00.
Continuity mistake: The flashing lights on the front of Bud and Jimmy's ambulance change places as they pull into the hospital driveway. They go from either the side of the hood to the front of the bumper.
Continuity mistake: Michael falls from the balcony in a different way from the first film.
Continuity mistake: Michael comes into Laurie's room and stabs at her bed, only to find pillows had been placed there. He then walks out and leaves the door open. When Jill returns from checking on a patient, the door is now closed and she opens it.
Continuity mistake: In the first scene when Loomis has just shot Michael. In first film, Loomis looks over the balcony and see that he is gone, but now he goes out and discovers that he is gone.
Continuity mistake: When Michael walks into the old couple's house, NIGHT OF THE LIVING DEAD is showing on the television. At that point, the film is just beginning, with Barbara and Johnny first pulling up to the cemetery. Much later in the film, the security guard is also watching NIGHT OF THE LIVING DEAD on television, and it's the scene where the cemetery zombie is attacking Barbara in her car. This is no more than ten minutes later in NOTLD, yet it's way more than ten minutes later in the evening of HALLOWEEN II.
Continuity mistake: At the end of the first film, Dr. Loomis looked down from the balcony to find Michael's body gone. However, in this one, he finds the body missing when looking out of the house's front door.
Continuity mistake: When Laurie runs away from Michael Myers in the boiler room, she climbs a window and falls into a storage room. Her hospital gown gets flipped as she falls, exposing her underwear. The close-up shows her falling again, this time without the upskirt shot.
Continuity mistake: Nurse Jill turns around before Michael Myers stabs her. After she's stabbed, she's already facing forward and her head doesn't snap to face the camera.
Continuity mistake: After Nurse Karen is drowned by Michael Myers, he drops her backward. The close-up shows however that she falls forward.
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.
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)
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.
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.