As small Mario, get behind Bowser and let him walk towards you. Jump, and try to land on the axe and Bowser at the same time. Bowser will hit the lava, as usual. Mario will "die" but he will angle towards the Mushroom Retainer and off the bottom of the screen. The Mushroom Retainer thanks you, and you move on to the next level. Note: This works in 8-4 also.