Event 15: The Hammer of the King
From SmashWiki, the Super Smash Bros. wiki
The Hammer of the King (デデデデデハンマー, Dedededede Hammer) is the 15th solo event match out of a total of 41 in Super Smash Bros. Brawl. In this event, the player plays as a tiny King Dedede with two other small Dededes as partners, and they must defeat a giant metal King Dedede. The battlefield is Smashville.
Finishing this event unlocks the track King Dedede's Theme.