Slenderman: scary, yes? Possibly the last thing I'd expect while playing something other than a Slenderman game. Oh, but he's out there, waiting, in Runner2 according to this video by Epsilonic.

Kind of the last place I'd expect him (it?) to appear, to be honest—then again, I'm not too far into the game myself.

Slender Man in Runner2: Future Legend of Rhythm Alien [Epsilonic]