Mamoo, Pooma and Kimo are three eighteen year-old, thousand-pound sumo wrestlers, dressed according to custom in super-hefty-size sumo thongs. In addition to their bulk, they pack ancient sumo powers and fight evil as 'Defenders of the Phat'. Regardless, when evil threatens, the three flex themselves into a dramatic physical transformation, doubling their size and strength. Together they fight against Ms. Mister and her henchmen Dr. Stinger and Geghis Fangus at Bad Inc. who are out to destroy the world.