The true antagonist and final boss of Kirby's Dream Land 3 for the SNES, who turns out to be the one controlling the Dark Matter monsters which were corrupting Pop Star.
It appears as a giant white ball with a single eye and is notorious for shooting projectiles made of it's own blood at Kirby and even more for ejecting it's eye in the final part of the battle.
Zero also appears (presumably) in Kirby 64, as Zero Two.