Split Mushroom (スプリット・マシュラーム?) is a troublemaking Mushroom-based Reploid in Mega Man X4. He was once in charge of operations at a Bio Laboratory, but when the lab was decommissioned he was disposed of. Mushroom was later resurrected by someone (assumed to be Sigma) and became a Maverick. During the Repliforce War, he reactivated operations at the Bio Laboratory and fortified it, attacking any invaders for fun and acting as a distraction to draw the attention of the Maverick Hunters. He apparently received orders to challenge and test X and Zero's abilities.