Continuity mistake: 10-year-old Michael has just returned home from trick-or-treating and is eating candy in the kitchen. The black handle of his pumpkin basket is raised in close-up shots while down in other shots.
Factual error: As Laurie, Linda and Annie are walking home after school, they pass several palm trees which are not typically found in Illinois.
Continuity mistake: Michael goes to his last meeting with Loomis bare faced and wearing a robe. Then he's sitting there not wearing the robe and wearing a mask.
Answer: He was hoping that Laurie would realise that she's really his sister. However, because Laurie was just a baby and raised by another family, she had no idea why Michael was showing her the picture or what it had to do with her.