Megahammer is a boss found in the game Super Mario Galaxy 2 in Bowser Jr.'s Fearsome Fleet. It is a giant robot with large hammers for hands operated by Bowser Jr., and vaguely resembles a Koopa Clown Car. The head of the robot is actually Bowser Jr.'s Robot Cockpit, which attached to the body prior to the battle.
It attacks by launching Bullet Bills and Banzai Bills. It also features a shockwave attack. To defeat it, the player must use Yoshi to catch the incoming Bullet Bills with his tongue, and spit them back at the robot's three blue orbs, two of which reside on its chest, while the last is found on its back. Players can use the Sling Star to get to the other side faster instead of walking around Megahammer. Once all three blue orbs have been destroyed, the metal plate covering the windshield of the Robot Cockpit head disappears. When Megahammer slams down its mallets, the player must use a Bullet Bill to hit Bowser Jr.'s cockpit twice.
Megahammer is fought twice, with the second fight being under the Daredevil Comet conditions.
Later in the game, Megahammer can be seen in Bowser Jr.'s Boom Bunker, broken. The chimney on Megahammer's cockpit has fire coming out, and if Mario attempts to jump into the chimney, he is burned and receives damage. The Toad Brigade is seen when first in the galaxy, hiding behind an arm. Megahammer is still functional, as Bullet Bills shoot out of it, and its eyes blink from black to red.
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