A skull monkey who helped Klayman stop Evil Engine Number Nine. He gave Klayman a root, which he used to put in the engine's exhaust pipe. Jerry-O was the only skull monkey who seemed intelligent, this may be attributed the the device on his head. He was able to bring Klaymen with a sort of space suit. He may have invented it. Klogg did not fool Jerry-O, as he did the others.