Leprechauns come from Irish folklore, where they're usually pictured as small, clever shoemakers with a hidden pot of gold. In many homes and classrooms today, especially in the United States, St. Patrick's Day has picked up a playful custom: children build a trap the night before, and in the morning they find it sprung, empty and surrounded by evidence.

The evidence is the fun part: green footprints, a tipped-over chair, a trail of gold-wrapped chocolates, a tiny note. The leprechaun always escapes, always compliments the trap and usually leaves a little treasure behind.

Keep it light. Compliance Unit mischief is small and easy to tidy: nothing broken, nothing spooky, nothing that would worry a child.