Fullmetal Alchemist - episode 29 - 23 Apr, 2004

The young boy who shadowed Edward and Alphonse on Yock Island is not only an alchemist, he is able to transmute his own body. After finding out about the scars on the boys right arm and left leg, Ed discovers that the boy is a homunculus who took his limbs during their failed attempt at human alchemy. (Source: Wikipedia)