Sisto is a villain on Space Ghost.
He first appeared on the 1960's show as Brak's second in command. He showed up on the episodes "The Lure", "The Looters", and "Two Faces of Doom".
Brak was never nice to Sisto. Sisto is afraid of Brak, and is a cat creature. In his first appearance he helped Brak kidnap Jace. In the end Sisto accidentally drives him and Brak into a hord of Pirranimites and they supposedly die. Sisto and Brak later returned to kidnap Jace for a second time. Space Ghost tharwted their plans and once again supposedly destryoed them. Sisto's last appearance on the show was in the fifth part of the Council of Doom episode where he tried to help Brak destroy Space Ghost but their plan failed once more.
Sisto returned to other media in one episode of Space Ghost Coast to Coast. It was revealed in that episode that Brak and Sisto were brothers.