Okay. If I remember right, this is what you do: Get Yoshi, then go back to the cliff that you start on. Then, hop down to those mushrooms that go below the village. Follow the path of mushrooms. Only jump to to the one closest to you. You may think you can make the jump, but you can't. Anyway, there is a green platform at the end of the mushroom path. Use Yoshi's juice to spray it, because there's some yellow moving crap-like stuff covering the hole. When it's gone, jump in the hole. That brings yoou to a retro stage involving lining yourself up so a Chuckster can throw you to another platform. Keep going, and you'll eventually get to the shine.
