Namahage

The Namahage is a Japanese boogeyman. People will often dress up as them to scare their children.

Legend
On the night of December 31, a band of adult volunteers--parents, teachers, clowns, whoever may be craving the sweet taste of a child's fear--dress themselves as shaggy, knife-wielding ogres and visit families door to door. It's sort of like grown-up trick-or-treating, except instead of yelling "trick or treat!" they're threatening the lives of little kids for all their disobedience over the past year.

Anything goes, really, so long as it strikes terror into little hearts. During each visit, parents get to gleefully play along as far as they're willing to go, stopping the 'devils' just short of dragging the kids away by mercifully promising that the kids will behave themselves and offering the monsters free alcohol instead.