WARNING: Do not use the super big mushroom or it might mess it up, and you need to be super mini mario!!!
When you get to the red turtle standing on the 3 boxes, STOP THERE!!! Then go to the 3 at the top, jump at the middle on, it's a secret vine there climb up it, you'll be on clouds. Now, while being super mini mario just keep running on the bottom cloud ( DON'T JUMP ON ANY OTHER CLOUDS!!! ) and when you fall from a cloud you just go back where you were, you should go under the other cloud at the bottom, at instead of falling... YOU DIE!!!