Event 3: Pink Ball Repulsion
From SmashWiki, the Super Smash Bros. wiki
Pink Ball Repulsion (ピンクだま潜入, Pink Ball Infiltration) is the 3rd solo event match out of a total of 41 in Super Smash Bros. Brawl. In it, Meta Knight must KO Kirby before the platform reaches the Halberd portion of the stage.
Clearing the event unlocks the Halberd trophy.