The first machine produced in Eggman's E-100 series, a line of highly accurate shooting robots powered by bioenergy from small animals. Though designed technologically superior to his younger "brother" Gamma, Beta quickly fell out of Eggman's favor after losing to the upstart Gamma in combat. Desperate for his creator's attention, the elder robot was allowed on board the Egg Carrier where he underwent a major upgrade. After the Carrier's fall, Beta - upgraded to E-101 Kai - was confronted by the rogue Gamma on the wreckage where the two rival robots destroyed each other.

E-101 Kai Beta's upgraded form, a cut above the rest of the E-100 series in both speed and strength.