Season 1 - Episode Guide

The League expands their operations, enlisting new recruits across the globe. The newest of these is Green Arrow, who has repeatedly refused to respond to invitations to join the League. He is therefore pulled to the rebuilt, and much larger, Watchtower by teleport. Opting against joining, he hitches a ride back to Earth with the team of Green Lantern, Captain Atom and Supergirl, who have been sent on a mission to stop a giant, uncontrolled, nuclear-powered defense robot in an unnamed Asian country existing in self-imposed international isolation.

Batman and Wonder Woman find Superman held captive by Mongul in the Fortress of Solitude and dreaming of an idyllic life on Krypton, courtesy of a wish-fulfilling parasitic plant known as the Black Mercy.

Morgaine le Fey transforms Superman, Batman, Wonder Woman, and Green Lantern into children after Mordred uses his magic to remove all adults from Earth and keep children on the Earth.

Wonder Woman teams up with two super powered brothers, Hawk and Dove, to stop Ares' plans to escalate a European civil war by loosing a war machine called the Annihilator into the fray.

The centuries-old enchantress Circe transforms Wonder Woman into a pig as revenge against Diana's mother. Batman and Zatanna work together to return her to normal, while B'wana Beast attempts to find the "Wonder Pig" before she's butchered at a slaughterhouse. It contains the famous scene of Batman singing the jazz standard "Am I Blue?" to a nightclub audience.

Supergirl, Green Arrow, and The Question investigate Supergirl's disturbing dreams. They discover that Cadmus created a clone of Supergirl named Galatea while she was recovering from her fight against Superman on Earth.

The Justice League battle Mordru in the background, while the narrative follows Booster Gold as he attempts to close a walking black hole while he's supposed to be on "crowd control".

The full power of the newly expanded League is unleashed for the first time while trying to keep Ivo's android Amazo from reaching his goal: vengeance against the recently reformed Lex Luthor. Luthor and the Atom attempt to create a weapon to neutralize Amazo's nanotechnology, though their victory is largely assisted by Dr. Fate.

The Justice League meets the Ultimen, a popular group of young heroes. The Ultimen discover they are the results of a government experiment in creating super humans and only have a short time to live. In frustration and anger, all but one Long Shadow strike out against the Justice League.

Most of the League battles with powerful alien nanotechnology, but realize that the waves of self-replicating robots cannot be simply destroyed. The diminutive Atom shrinks himself to stop the robots from the inside.

A trio of high school kids accidentally resurrect Solomon Grundy, reviving him more powerful than ever but with no memories of his past. Dr. Fate, Amazo, Aquaman, and Shayera assist League regulars stopping his rampage.

Batman, Wonder Woman, and Green Lantern chase Chronos to the past, where they team up with some of the greatest DC heroes of the Old West. After defeating stolen future tech in that era, they again follow Chronos to the future. Warhawk from the Batman Beyond era is revealed to be Green Lantern's and Hawkgirl's son.

Batman, Green Lantern, and Wonder Woman chase Chronos into the future Gotham City of Batman Beyond, just in time to face a battle with a group of Jokerz beside that era's Justice League. The time travelers are taken to the Justice League Unlimited refuge. An older Bruce Wayne reveals the street gang they fought together was enhanced by Chronos who led them to kill the rest of the League of that era. The combined heroes defeat the retooled Jokerz, and Batman traps Chronos in a time loop.