Disclaimer: Knowing full well there is a wealth of resources available to fans of the "Justice League" animated series, I have no intention of doing a bunch of dry story synopsis with the occasional new screen grab. I will chronicle, within reason, J'Onn J'Onzz's specific journey over the course of the series, but chiefly I will be reviewing the episodes through my own jaundiced perceptions.
Superman and the Martian Manhunter are working to redirect a meteor bound for Earth when they’re caught in an explosion. Their unconscious forms are picked up by some especially well designed random aliens, who take the pair of heroes back to their master on Warworld. The atmosphere there effects J’Onn J’Onzz negatively, leaving him nearly helpless. Superman has no such affliction, as he saves J’Onn from a massive “croc” and aids him in escaping a slave pin. The heroes fly outside, but while the weakened Manhunter sails past, Superman smashes against a force field, confining him in a coliseum. The Man of Steel demands the Martian leave him and seek help, which J'Onn does only after Superman is recaptured.
Who rules Warworld? Mongul rules Warworld! The jaundiced tyrant hews closer to the Post-Crisis revamp of the character than the original Darkseid/Darth Vader/Yellow Peril hybrid, the main plot borrowed liberally from the first major Post-Byrne story arc in the Superman titles. However, as with his first appearance in the comics, the pair of Manhunter and Superman seem poised to battle Mongul, but it becomes swiftly evident this is really just a Superman story.
Mongul believes that he can overlook social issues on his artificial planet, so long as he distracts the masses with brutal arena competitions. Unfortunately, no one can truly challenge his champion, Draaga, until a certain Kryptonian is forced into combat. In the crowd, a concealed Martian queries, “So many spectators... don’t they have families or jobs to tend to?” On learning that no, they do not, he exclaims, “How dreadful.” J’Onn repeatedly expresses concern as Superman is increasingly bruised and bloodied, but the Kryptonian is ultimately victorious. More importantly, Superman refuses to slay Draaga, against Mongul's direct order, and thus earns his enmity.
From the stands, in a particularly awkward reading from Carl Lumbly, Manhunter leads the audience in a chant of “Superman!” To avoid inciting the masses further, Mongul spares Superman’s life, though still making him a popular symbol of rebellion. To save face, Mongul threatens to destroy a world unless Superman throws an arena fight against him. A stealthy Manhunter overhears the extortion demands, and sets about disarming the planet smashing laser by impersonating Mongul. The gambit encounters misfortune, as the Martian is too hobbled to maintain the form, and barely escapes with his life. The tide turns, however, when Hawkgirl and Green Lantern finally locate their wayward cohort. The laser is destroyed, and with it, Mongul’s hopes of defeating Superman. Draaga returns to knock out the former ruler of Warworld, and Superman convinces him to assume the role himself.
Per his filmography, Eric Roberts seems inspired casting for Mongul, but his drawl in my opinion tended to diminish any presence the villain might have had, reducing him to little more than an overconfident crime boss. William Smith fares better as the distinctive Draaga. Stan Berkowitz's script guides Superman into the welcome embrace of Gladiator machismo.