WARNING: You will need to use the Dry Bomber to do so.

First, pick anyone with the Dry Bomber and then go to the DK Pass. Once you get past the falling snowball, go up the small snow hill, you will see a block there. Hit the block, and you will get Triple Mushrooms or a Star! You will even get Triple Mushrooms and Stars when you are in First Place! This secret is useful to get back into the game, or just to get very far ahead of all the other racers.

I hope this trick helps!