This only works during the Shyster attack that happens early on in the game, in the Mushroom Kingdom. Go to the building with the kid jumping on the bed (it's in the upper-left corner). Save the kid's family by killing the two Shysters. Then, go upstairs and kill the Shyster jumping on the kid's bed. The father will thank you, give you a prize, and then encourage his son to keep on jumping. the boy will start jumping rapidly. Now, jump on top of his head and jump up and down. Eventually, he will sink into his bed and then after you jump a bit, he'll end up almost through the ground. Strangely, his shadow will stay on the bed. And, the bed will not be springy like other beds in the game. This doesn't seem to work at any other time when he begins to jump rapidly.
Submitted by: Glitched Symbols