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, that vaguely resembles a Koopa Clown Car. From what is known, it attacks by launching Bullet Bills and Banzai Bills. 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.

Trivia

 * Megahammer was originally going to be called "Mallettoid", but this was changed before the final version of the game.