Continuity mistake: After Ben Tramer gets hit by the police car, his body can be seen and heard slumping. In the next shot, he is pinned fully upright.
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.
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.