Mario makes bouncing around on precarious surfaces look so easy, but anyone who's participated in the new viral 'milk crate challenge' probably has the scars to prove otherwise. The rules of the milk crate challenge are pretty simple—all you have to do is walk up and down a wobbly makeshift staircase of milk crates without falling on your face. Although some freaks with excellent balance and core strength have managed to make it look easy, in most cases, those who accept the challenge end up pl…