Super Mario Galaxy 2/Throwback Galaxy

Star 1: Return of the Whomp King
When you finish this level, a Bob-omb Buddy will appear on Starship Mario.

Jump on the grey wall with an yellow arrow on it and follow the other arrows. Turn left, go on the short passage or the rock bridge, which disappears if you walk on it. Go on the moving bridge and run to the big mauve piranha plant. Kill it if you want and go up with the elevator. Defeat the Whomp to reveal a passage to the real fight with the Whomp King. To defeat it you have to wait until he tries to crush you. Avoid his attack or you will die immediately. When he is dizzy do a ground pound on his back. Do that three times to defeat him and you will get the star. Just be careful of the Mini-Whomps who appear after you strike it the first time.

Comet Medal: The Comet Medal is below the flag with the 1-UP mushroom on it.

Star 3 (Prankster Comet): Whomp Silver Star Speed Run
Repeat Star 2 within a time limit of 2 minutes.