Event 28: Puffballs Unite!
From SmashWiki, the Super Smash Bros. wiki
The player can choose a character to defeat 14 Kirbys (4 at a time) on the Green Greens stage. This event match is similar to the match in Adventure Mode, where each of the Kirbys is wearing a Kirby Hat, giving every Kirby a unique neutral special move. The Kirbys in this event are heavier than in Adventure Mode. This event has a rather strict time limit of 2 minutes, where the event will end in failure if the player fails to KO every Kirby within that time limit.