Need a glitch for a horrible, wonderful, awful prank

I want to freak out my friends with a "ritual," where I basically do some fake chanting and stuff, then trigger some kind of glitch to make them question reality and stuff

Only thing is I have no idea what would be good for that

Are there any exploits, bugs, or glitches with recent versions of java that would make for a cool glitch to activate? Preferably something that's not \*as\* widely known?