In the playground of the questionable area, theres a couple of Rocking... Lumberjacks. The physics on them is hilarious, yet questionable at best when you hit them. However if you do a slam attack on top of one, theres a decent chance that it ends up clipping you through the floor and out of the world, where you fall forever until you return to the main menu or exit the game. There doesnt seem to be any sort of lower limit Out of Bounds that stops your fall and brings you back up.