Super Mario Galaxy 2/Boulder Bowl Galaxy

Star 1: Rock and Rollodillo
Grab the Rock Mario power-up and head over toward the 6 creatures that look like bowling pins. Knock them all down, then proceed toward the ramp with a double-chevron on it. Roll towards the ramp and you'll be launched to another planet.

After defeating each of the rock-spitting creatures, a Launch Star will open, sending you toward a planet with Chain Chomps and Lodestones. Transform into Rock Mario again and roll towards the purple crystal containing a jump star.

Now on the golden translucent planet, tag the checkpoint flag and power-up with the Luma Shop before using the Launch Star to continue your journey.

Mini Boss: Rollodillo
On the wire mesh planet, you'll be faced with a Rollodillo.

Transform into Rock Mario and roll into the Rollodillo's exposed tail four times to defeat it. Avoid the spines and nose, as you'll not only lose your rock power-up, but also a life wedge with each collision.

Grab the Power Star and return to Starship Mario.

Star 2 (Prankster Comet): Rolling Crabber Romp
This mission requires you to bowl over all of the crabbers within one minute. Crabbers cannot resist a rock mario attack, so always have mario in his rock form. Each blue crabber will release a green 1-up mushroom.

Star 3 (hidden): C'mere, Goomba
This Star is only available when you get a letter from Gearmo.

Enter Star 1 and go to the third area. Find the golden gearmo and he will give you your mission. Roll into one of the sharp tall rocks to release a goomba. Let the goomba follow you all the way back to the gearmo.

When you finish this level, Gearmo will appear on Starship Mario and will give you a 1-up for all of your troubles.

Green Star 1
This green star is very hard to reach. In the first area, do not bother freeing the rock mushroom and head straight to the metal bridge. Wall jump off of the red railings to get to the very top of the bridge. Use a spin after every wall jump to gain the necesary height. At the very top, you will see the green star. Use a backflip to reach up and take it.

Green Star 2
The Second green star can be found right in front of the launch pad near the pinheads in the first area. Use the rock mushroom to knock down the bridge. Do not roll forward, instead walk past the pinheads and walk right off of the ramp. You should fall into this star.

Green Star 3
After shooting off the ramp, you should arrive in the second area with the pink octoombas. Go to the other end of the planet where you will find a green octoomba and a rock mushroom. walk past the wooden fence past the green octoomba and you will land into the green star.