A video called Crazy Flying Snowball Prank is big on YouTube right now.  It's two guys walking around a college campus, trying to freak out strangers by throwing snowballs at them.

But they're not actually holding snowballs . . . they're holding white balloons.  So when they throw them, first the people shield themselves, then start laughing when they realize it's just a prank.

Campus police step in toward the end of the video, worried that any popped balloons might freak people out.