KO Stars

From SmashWiki, the Super Smash Bros. wiki

KO Stars (also called Knockout Stars) are an "award" for defeating an opponent(s) in the VS. Mode of Super Smash Bros. Melee and Super Smash Bros. Brawl The amount of KO Stars you have are dependant on the amount of opponents you have defeated, For example, if you knockout two opponents, you recieve two KO Stars. The game allows you to only have 255 KO Stars at a time, any knockouts achieved after you have 255 will not reward you a KO Star. KO Stars cannot be kept permanently, and are "removed" once you exit VS. Mode or change your username. If you exit VS. Mode, all characters will lose any they have earned. Computer controlled players do not earn KO Stars.