From the back of the book: The Thundercats RPG is an extremely compact RPG...based on the core concepts of the 1980's Thundercats franchise. [Thundercats: the Role-Playing Game] is a not-for-profit fanwork only. Thundercats: The RPG is a game about the struggles of the heroic Thundercats to survive and thrive in a world populated by Mutants and the dreaded Mumm-Ra. Players take on the roles of classic Thundercats or create their own heroic anthropomorphic cats from Third-Earth.