Super Mario Galaxy Easter eggs

Hidden planet at the good egg galaxy!
First, make sure you do the mission Dino piranha or you will not go to the right planets. After you go from the starting planet to the one with the rock balls, and to the small green one with the vine, you should come to a large green planet that also has rock balls. Right after you start, head in the diction the rocks are rolling until you come to a brick type platform on the edge, to the right. Jump on this and there will be a square green platform to go on that shrinks when you step on it, jump across it to the other side, and there will be a warp pipe with a piranha plant in it. Defeat the plant, jump in the pipe and you will be warped to a secret planet. There will be a life, and when you make all the platforms green a launch star will a peer, which takes you back to the green planet.