Megahammer

Megahammer is a boss in Super Mario Galaxy 2, which appears at Bowser Jr.'s Fearsome Fleet. It is a giant robot operated by Bowser Jr., which vaguely resembles a Koopa Clown Car.

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 orbs are destroyed, the protection on Bowser Jr.'s control in the robot's 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 would be burned and receive damage. The Toad Brigade is seen when first in the galaxy, hiding behind an arm. Megahammer is still alive, because Bullet Bills are shooting out of it, and its eyes are blinking black to red.

Trivia

 * Megahammer was originally going to be called Mallettoid, but this was changed before the final version of the game.
 * The yellow and black designs on Megahammer's arena break off when attacked by Megahammer. If Megahammer's hammer or a Bullet Bill hits these designs, it would fall off creating a gap Mario or Luigi would have to jump over. The yellow and black designs are unaffected by Megahammer's shockwaves because the shockwaves are in the air and not on the ground.
 * Megahammer resembles Mechawful from Mario & Luigi: Bowser's Inside Story.