Select Kirby as your character in the player select screen. Then go to the edge of the platform. Make sure your opponent is near the edge also. Face the opponent and jump backwards off the edge. Just before you start to fall press B. That will make Kirby swallow that person. Kirby will slowly drop with the enemy in its mouth. Hint: Don't press down on the controll stick while Kirby is falling or he will swallow the enemy.