Go to the level "Don't Look Back" (I think level 4-3). Get to the end of the level and go to the area with the large balloon that you blow up. If you stand next to the balloon and hop lightly on the very left edge of the pump and then fall off, it will make a noise as if you are pumping the balloon, but neither the pump nor balloon will move. Even if you do this repeatedly, the balloon will not fill with air.
Now, pump up the balloon to its largest and let it fly. If you run under it, on the land below it, and jump and hover up right under it, you will go inside of it and then somehow hop through it to the top. This is useful if you fall off at the beginning of the ride and want to get back on.
Submitted by: kornyhatemachine