 The original series story revolves around a group of humanoid cats who must flee their planet of Thundera after it s destroyed. Once crash-landing on another planet, Third Earth, they must thwart Mumm-Ra, an evil sorcerer, bent on killing them off. Sopocy s script is described as an origin story expanding on the major heroes and villains from the animated series, with the plot focusing on Lion-O coming of age as the leader of the Thundercats