Hint - Toad #3 (World 2, Level 3)
Go to the tube at the end of that grassy land/area go down the tube that works. After that, go down and to the right until you reach the bottom. Then you cry on the wheel until the caption says something about a loud noise. Then go to the right and into that tube.

You end up at around the same area you statred. Go down the tube you came up in and go down past the two chompers, or until you reach a tube sticking out from the ground. Go down that tube and then go to the right. Watch out for the big bullet dudes! Keep going right until you see the toad's box in the small space between those breakable boxes.