Bullet Bill on Your Back

Bullet Bill on Your Back is the sixth mission of the Dusty Dune Galaxy in Super Mario Galaxy. It is a hidden mission accessed through the Sunbaked Sand Castle mission.

Layout
The player needs to go through the original mission as normal until they reach the Sand Tide Planet. The sand on the planet will rise and lower, and a stump will be revealed at the lowest tide. Ground Pounding the stump will cause Rainbow Notes to appear around the planet, and collecting them all will cause a Launch Star to appear.

The Launch Star will take the player to a second disk planet with a Bill Blaster that shoots out two Bullet Bills at a time. Ground Pounding a switch will cause a platform to rise underneath the Bill Blaster and breakable cages will appear around it, which contain Star Bits, a Rainbow Star, or the Power Star. The player needs to lead a Bullet Bill into the cage with the Power Star in order to claim it. Ground Pounding the other switch will cause the platform and cages to lower if the player needs to do so.