Boo Mushrooms are power-up mushrooms that debuted in Super Mario Galaxy. It reappears in Super Mario Galaxy 2. It is only first found in the Ghostly Galaxy of Super Mario Galaxy, where Mario must use it to navigate through a large mansion. Upon using this mushroom, Mario or Luigi can transform into a Boo, becoming Boo Mario or Boo Luigi. In this form, the brothers can achieve invisibility for a few seconds and have the ability to pass through certain walls. To float progressively upwards, the player needs to repeatedly press A on the Wii Remote. Mario can be reverted to his original form by touching a source of light or touching at enemy. While in this form, Boos will chase Mario out of love. With this ability you can find a Luigi Easter egg!