In the '70s and '80s, DC's greatest superheroes were defined by the kid-friendly Super Friends animated series. But in 2001, Cartoon Network's Justice League animated series changed the game and arguably paved the way for the MCU and the DC Extended Universe. The Justice League series was a direct continuation of Batman: The Animated Series, Superman: The Animated Series, and Batman Beyond. It even incorporated Static Shock into its shared universe.
Bruce Timm co-created the previous Superman and Batman animated series in the '90s. But in Justice League, Timm had even greater freedom to expand his roster of heroes and villains. Most notably, Timm and his creative team tweaked the Justice League lineup to increase its diversity. That's John Stewart was Earth's Green Lantern, and Hawkgirl was on the team instead of Aquaman.
For 52 episodes, the Justice League rest took on DC's top villains. Lex Luthor, The Joker, Brainiac, and Darkseid were all fair game. The show's voice cast was also second to none. Kevin Conroy reprised his role as Batman, while George Newbern took over as Superman. Susan Eisenberg was cast as Wonder Woman, with the incomparable Phil LaMarr as John Stewart. Smallville's future Lex Luthor, Michael Rosenbaum, co-starred as The Flash, with Carl Lumbly as Martian Manhunter and Maria Canals-Barrera as Hawkgirl.
Although Justice League lasted only two seasons, it quickly returned to Cartoon Network as Justice League Unlimited, a series that featured even more heroes. But that's a story for another time.
For more Justice League details, check out the latest episode of SYFY WIRE's Everything You Didn't Know!