|Jafar says: Read my lips and come to grips with the reality!|
Bouldergeist is a sub-boss from Super Mario Galaxy and Super Mario Galaxy 2. It is a huge rocky creature made of rocks and matter who kidnapped Luigi and trapped him in the Haunted Mansion. Additionally, it is the reason why Luigi was separated from the Toad Brigade and got lost in the Ghostly Galaxy.
Bouldergeist is a gray rocky creature with horns and yellow eyes. Its hands are also gray.
In its true form, which is revealed when Mario weakens it with Bomb Boos, Bouldergeist is much smaller and has a red uvula with a black face.
Boldergeist is fought in the stage "Beware of Bouldergeist", where it is on the final planet. Bouldergeist can create rocks from its matter to crush Mario; some are colored golden and contain coins, while others are black and contain Bomb Boos. To defeat it, Mario will have to spin two Bomb Boos towards it via his Star Spin to destroy its rocky armor and a third to damage it while it is reduced to matter. After this, it will reform, but now with two large floating rock hands. It can swipe and slam its hands, and even create stalacites that will damage Mario if they spawn under him and act as obstacles to him, but that he can destroy using Star Spins or Bomb Boos. Mario does not have to destroy the arms, but he will have to destroy its face again, which the hands make harder to do due to the fact that Bomb Boos will also explode if they hit them instead of its face. Once its uvula-like core is hit with another Bomb Boo, the boss explodes and exposes the Power Star.
If a Daredevil Comet lands in orbit of the Ghostly Galaxy, Mario must face Bouldergeist again with only one hit point, and Bouldergeist will not throw golden rocks. Defeating it under these conditions awards Mario with another Power Star.
In Super Mario Galaxy 2, Bouldergeist is the fourth boss fought in the Boss Blitz Galaxy, and its defeat creates a Launch Star that leads to the next planet, where Fiery Dino Piranha is fought.
- Bouldergeist's name is a combination of "boulder" and "poltergeist", basically meaning "Ghost Boulder".
- In its true form, Bouldergeist resembles Cackletta's soul.
- Its appearance was inspired by Bogmire, the second boss of the GameCube's video game Luigi's Mansion.