Boo in a Box

Boo in a Box is the hidden sixth mission of Deep Dark Galaxy in Super Mario Galaxy. This mission can be done during any standard mission.

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The player must make their way to the bottom of the underwater cave and find a Green Shell. Launching the Green Shell at one of the Mikey Mines surrounding the broken ship mast will cause them all to explode, revealing a Launch Star. The Launch Star will send the player inside of a floating box with a single Atomic Boo and a Ground Urchin inside. Flipping the arrow to change gravity until the player is on the wall to the right, the player will find a crystal blocking a hole. Shattering the crystal will let in light and the player then has to lure the Atomic Boo into the light, causing it to be defeated and dropping the Power Star.