In World 1-1, hit the "?" block containing the Mega Mushroom, then run as fast as possible to the end of the level and smash everything in sight. If you crash all the way through to the flagpole, you can earn up to five 1-Up Mushrooms. Enter the world again and repeat this as much as desired.

In World 6-6, when you find five pipes at the end of the level, go in the third pipe. You will get shot out to the top of the flagpole.