Voltron: Defender of the Universe

Planet Arus has an evil twin planet, Pollux, that has allied with Zarkon. The Voltron Force travel to Pollux in an attempt to make peace. They meet the high strung younger prince, Bandor, and his sister Romelle -- who bares an uncanny resemblance to Princess Allura. But the king's first son, Avok, volunteers to become a Robeast to fight Voltron. Because he is willing, the evil Haggar is able to make him the most powerful Robeast yet!