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 weak points, 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.

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 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 second part of the fight with Megahammer requires firing Bullet Bills at the cockpit that Bowser Jr. is in. Doing this 3 times will release the Grand Star.