Boo Mario

In Super Mario Galaxy this is a form Mario takes from a power up. It can only be found in the Boo galaxy. Mario must find it to save Luigi in a ghost mansion. By shaking the Wii remote you can make Mario transparent and walk trough some walls. He can also levitate a little higher. If Mario is hit by light he will revert back to normal. Also you race a Boo across a obstacle course and use this form to help.