The Mushroomized Mainbrain is an enormous robot corrupted by spores spread by the Puffstools. It is the boss of the G-Base and it must be defeated in order to save the President (who is actually the second-to-last treasure in the game!) The boss is defeated before the end of the game, but it is not listed in the Piklopedia because it is not native to the Pikmin planet. The Mushroomized Mainbrain and the various machines it controls- G-Pods, Drilling Diggers and the like were scrapped equipment left behind on the Pikmin Planet as space trash by the All-Devouring Black Hole Loan Sharks.