1. Halloween was on a Sunday.
2. It rained on Halloween.
3. "That House."
4. Neighborhoods who don't hand out candy to kids they don't know.
5. Reports of a creepy guy hanging out by the park.
6. That one kid who wore that costume last year that canceled this year's costume day at school.
7. Blizzard hits on Halloween.
8. You accidentally awaken an ancient troll curse that terrorizes the town.
9. Falling down the steps.
10. Older kids trick or treating.
Some suggestions provided by the insanely talented Matt Lamson.