The greatest heroes in comic book history join forces in this animated made-for-TV adventure. After the United States sends an expedition to Mars, one of the astronauts, J. Allen Carter (voice of Gary Cole), runs for president, and after taking office makes good on a promise to eliminate nuclear weapons, calling on Superman (voice of Kevin Conroy) to use his powers to protect America instead of the bomb. Superman agrees, but he soon he and his fellow superheroes find themselves battling a strange and mysterious force. Superman and Carter are approached by J'On J'Onzz (voice of Carl Lumbly), who was one of the few survivors of a war that destroyed Martian civilization after the Earthlings visited. J'Onzz informs Superman that a sinister cadre of fellow Martians has made their way to Earth with plans to take over the world, and that they must be stopped if the people are to survive in freedom. Superman prepares for the fight of his life by bringing together a team of the greatest defenders on Earth, including Batman (voice of Kevin Conroy), Wonder Woman (voice of Susan Eisenberg), Green Lantern (voice of Phil LaMarr), the Flash (voice of Michael Rosenbaum), and Hawk Girl (voice of Maria Canals). Justice League: Secret Origins was the pilot film for the animated television series, and was divided into three episodes for broadcast on the Cartoon Network.