Prototype for Eggman's E-100 series, a line of highly accurate shooting robots powered by bioenergy from small animals. Unlike later models, ZERO lacks a laser rifle and instead fires its bulky, powerful fists like rockets. The lumbering, ape-like machine lacks both patience and intellect, pounding the ground furiously whenever it loses sight of its target. Its unrelenting pursuit of an Emerald-bearing bird kept self-proclaimed guardian Amy on her toes in Sonic Adventure. When the machine finally landed a smack on the helpless tweeter, the infuriated Amy smashed the mecha brute to bits with her Piko-Piko Hammer.