According to producer
Bruce Timm, the
series finale of
Justice League, "Starcrossed", was possibly meant to be the final episode of the series; however,
Cartoon Network ordered the production of season 3 and 4. The network wanted the show to be rebranded, including changing the episode format, so instead of two-part episode stories, the standard half an hour format was used. Additionally, alongside the name change, the show features a greatly expanded League, in which the characters from the original series—now referred to as "founding members"—are joined by many other
superheroes from the
DC Universe; in the first episode, well over 50 characters appear. A number of these were heroes who had made guest appearances in
Justice League, but many heroes and other characters made their first animated appearances in this series. The general format of each episode is to have a small team assemble to deal with a particular situation, with a focus on both action and character interaction. This extension of the
Justice League was originally planned to be explained in a
planned direct-to-video feature film, but the project never materialized.
Production Justice League Unlimited features both episodic and serialized episodes, the first major overarching story arc involves the growing conflict between the League and a secret government agency known as
Project Cadmus. This plot line builds upon events that occurred during the second season of
Justice League (which in turn built upon events in
Batman: The Animated Series,
Superman: The Animated Series,
Batman Beyond,
Static Shock, and
The Zeta Project), and would go on to affect the plotlines of most of its episodes. It was resolved in a four-part story at the end of the second season of
Justice League Unlimited. The third and final season story arc focuses on the new
Secret Society, a loose-knit organization formed to combat the increased superhero coordination of the first season. Towards the end of the series, certain characters became off-limits to the show, particularly characters associated with Batman, were restricted due to the unrelated animated series
The Batman and
Christopher Nolan's live-action
The Dark Knight Trilogy, to avoid continuity confusion, thus leading to the popular term known as "Bat-embargo".
Aquaman and related characters were unavailable due to the development of a
pilot for a live-action series featuring the character as a young man (planned to be a spin-off of
Smallville). To compensate for this, the last season focused their stories on previously overlooked
DC Comics characters and mythos. These included characters like
Deadman,
Viking Prince, and
Warlord. The series, along with the entire DC Animated Universe, was originally planned to end after the second-season finale "Epilogue", which concluded the story of
Batman Beyond and thus the entire DCAU chronologically. But a third season was greenlit by Cartoon Network. The third season started in 2005 with the episode "I Am Legion" (which was written before the announcement of a third season) and ended in 2006 with the episode "Destroyer". Stan Berkowitz, a member of the production team, left the show later for the TV series
Friends and Heroes, and writer Matt Wayne was contracted to replace him. According to Wayne, if the show had been renewed for a fourth season, he would have liked to write more episodes focusing on
Superman and
Wonder Woman. DC Comics created an ongoing monthly comic book series based on the TV series, as part of its
Johnny DC line of "all ages" comics, which did not have the same restrictions regarding character appearances.
Justice League Unlimited, like the second season of
Justice League, is animated in
widescreen. The show also features new theme music and intro (nominated for an Emmy). The two-part
series finale was aired in the UK on February 8 and 18, 2006, and in the United States on May 6 and 13, 2006. ==Episodes==