I've said it once and I'll say it again: Don't piss off Slendy. Or he will destroy the world.
I actually thought of this during class, so I had to try not to laugh.
Soooo . . . When's the world ending then?
I dunno, maybe a couple more centuries. Then the world will slowly start to end. I'll make them think it's global warming until the last moment -evil laugh-
EDIT: Forgot to write this when first writing the description: No, I don't think Slendy would actually have to power or want to end the world, he just likes having authority