Bouldergeist

Bouldergeist is a boss in Super Mario Galaxy. Mario faces him in the area known as the Ghostly Galaxy.

Bouldergeist looks like a bunch of rocks stacked together into a stone column. However, his true form is in actuality a small black ghost with a red bubble underneath him (possibly his uvula). In order to defeat him, Mario must use Bomb Boos to break apart Bouldergeist's rocky exterior and hit his red bubble with another Bomb Boo.

When Bouldergeist shapes two rock hands, some of his attack pattersn are similar to Eyerok, another Mario boss.