Boo Mushroom

The Boo Mushroom is a type of Mushroom which appears in Super Mario Galaxy. It's a white mushroom with a Boo-like face. When Mario obtains this Mushroom, he will transform into Boo Mario. These Mushrooms are mostly found in the Ghostly Galaxy.

The mushroom first appeared in the level titled "Luigi in the Haunted Mansion".

Trivia

 * Luigi is shown to dislike this item. When Mario uses it, Luigi mistakes him for a real Boo and is frightened by him.  Later, when Luigi uses it, he frowns.