Prank Idea: Costume Party
Scale and theme are the watchwords here. 10 students showing up to school dressed in Halloween costumes is fun-weird, but 100 students showing up dressed as zombies (or storm troopers, or Batman) is amazing. Our favorite idea is getting everyone to wear Homestuck troll horns. Because there's a tipping point at which it becomes more disruptive to have everyone change than to just let them stay in costume, if you can get enough people involved, there's a decent chance you'll get to stay in costume all day.