Twenty years ago, on November 17, 2001, Justice League premiered on Cartoon Network. Animation legend Bruce Timm produced it, and it was a sequel series to both of his weekday afternoon cartoons  Batman: The Animated Series and Superman: The Animated Series. Fans practically begged for this show for the better part of a decade. And when it arrived, it truly delivered.  Timm and company created a show which was a love letter to DC Comics lore. The animated Justice League was filled with fun facts, trivia bits, and easter eggs, and fans simply ate it up. And they loved it all the more when it transitioned into the more expansive Justice League Unlimited series in 2004.

For its twentieth anniversary, we present ten interesting details about Justice League, the animated tv show, that even some of its biggest fans might not know.

Justice League’s Marvel Comics Connection 
DC's Amazon, and Marvel's Adam Warlock.
Warner Bros. Animation/ Marvel Comics

Justice League was a celebration of DC Comics heroes, but the producers were also big Marvel Comics fans. And they snuck in a couple of big Marvel references, some that many fans missed. For example, in the episode “ Tabula Rasa,” we meet the android Amazo, a longtime DC villain who could absorb the League’s powers. For Justice League, he got a complete redesign, and his storyline now matched that of Marvel’s Adam Warlock. Both were androids created by mad scientists, who then departed for the cosmos and evolved into godlike beings. Amazo even became golden-skinned, just like Warlock.

Warner Bros. Animation / Marvel Comics

Another big Marvel nod came in the episode “Wake the Dead” from Justice League season two. The episode featured a team lineup that reflected the 1970s roster of Marvel Comics’ Defenders. That long-running comic featured Doctor Strange, the Incredible Hulk, Namor the Submariner, Silver Surfer, and Valkyrie. So Justice League gave us the DC equivalent. Dr. Fate stands in for Doctor Strange, Solomon Grundy stands in for Hulk, Aquaman is Namor (naturally),  and Hawkgirl serves as Valkyrie. Much like the Defenders comics, Grundy calls Aquaman “dumb fish man,” just as Hulk would call Namor.

DCEU Wonder Woman Borrowed Elements of Justice League’s Diana
Warner Bros. Animation.

Wonder Woman’s origin story has remained roughly the same from decade to decade. It goes like this: Pilot Steve Trevor crashes on Paradise Island, and Diana must fight in an Amazon contest to prove her worth to leave and go to Man’s World. Once she wins the contest, the Amazons gift her with the Wonder Woman costume and weapons.

But in the Justice League pilot “Secret Origins,” when Diana’s mother forbids her to leave Themyscira, she steals the armor and weapons in the dead of night instead. Patty Jenkin’s Wonder Woman used this same story detail, one created for the Justice League cartoon years earlier. An interesting Justice League fact many may have missed.

All The Super Friends References in Justice League
Warner Bros. Animation

The long-running Super Friends cartoon was the definitive version of DC’s heroes in animation for many fans. But when Justice League rolled around, Bruce Timm and the other producers wanted to steer clear of that staple of Saturday morning TV. The show had such a goofy reputation that they hoped to avoid any connections to it (aside from a Super Friends joke Flash makes in the pilot).

But try as they might, they could not deny the power of Super Friends. In the JLU episode “ Ultimatum,” they introduced the Ultimen, a direct reference to the “created for TV” Super Friends characters like Samurai and the Wonder Twins. And in the final season of JLU, the consortium of villains use an HQ that looks just like the Legion of Doom’s from 1978’s Challenge of the Super Friends. Meanwhile, the League’s Earth-bound base, the Metro Tower, looked exactly like Super Friends’ Hall of Justice. No animal sidekicks like Gleek the monkey or Wonder Dog, though. This is a shame because they could have made for great Justice League Easter eggs.

The Justice Society Were Not Allowed to Appear in Justice League
Warner Bros. Animation

In the pages of DC Comics, before there was ever a Justice League, there was a Justice Society of America. The original heroes from World War II lived on the parallel world of Earth-2 and would fight alongside the JLA for decades. But in the first season episode “ Legends,” when the League crosses over into a parallel world representing a bygone era, the heroes are the Justice Guild of America, not the Justice Society.

So why the change? Despite all being thinly veiled versions of the JSA, DC Comics president Paul Levitz believed the episode as written poked too much fun at the characters. It definitely made them seem dated and anachronistic in many ways. And he didn’t want to see them become jokes to a new generation. So the JSA became the JGA. In later seasons though, many actual JSA heroes like Wildcat and Hourman would become JLU members.

Batman Beyond Led to Justice League, the Animated Series
Warner Bros. Animation.

After Batman and Superman’s series, fans constantly asked Bruce Timm, “Is a Justice League animated series next?” And he always maintained, for nearly five years, that a Justice League show would have too many characters and be too unwieldy to produce.

But towards the end of the production cycle for Batman Beyond, Timm and company introduced a future version of the JLA, called Justice League Unlimited. They appeared in one of the last episodes of that series, “The Call.” That episode proved they could do proper team action and do it well. A Justice League show now seemed possible, and they were off to the races. How is that for a Justice League fun fact?

Justice League’s Space Base the Watchtower Is a Mashup
DC Comics / Warner Bros. Animation

In the animated series, the Justice League had an orbiting space station base overlooking the Earth called the Watchtower. But it’s actually a combination of two iconic locations from the comics. The first is the JLA Satellite, the space station that served as the team’s HQ. Spinning in geosynchronous orbit, some 22,300 miles above the equator, this was the team’s home from 1970-1984.

Meanwhile, in Grant Morrison’s seminal ’90s JLA comics run, he introduced the Watchtower, the team’s base on the moon. Bruce Timm combined these two concepts by making the Watchtower an orbiting space station. It proved so popular; the comics followed suit.

Many DC Heroes Were Off-Limits to Justice League
Warner Bros. Animation

Despite the JLU eventually boasting some sixty members, several iconic heroes were still forbidden from appearing on the animated series. Licensing issues (and paying creator royalties) kept long-standing members from the comics away. For example, Firestorm, Blue Beetle, Black Lightning, the Spectre, and more were unable to appear. Also, because of the production of the non DCAU affiliated series The Batman starting in 2004, all ancillary Bat-sidekicks and villains could not show up while both shows were in production.

However, in the episode “ Grudge Match,” the producers snuck in the silhouette of Nightwing watching over his hometown of Blüdhaven. So he’s there if you look for him. Since Justice League Unlimited ended in 2006, all of these various rights issues have been resolved. Later, these characters appearing on more kid-oriented shows like Batman: Brave and the Bold and Justice League Action was permitted. If they ever made an animated Justice League reboot, they would have no problem showing up.

Justice League’s Green Lantern Informed the Comics
Warner Bros. Animation

First appearing in the early ’70s, John Stewart became Hal Jordan’s alternate Green Lantern whenever he couldn’t use the ring. This made him DC’s first prominent African-American superhero. When Bruce Timm decided to tackle Justice League as a series, he chose Stewart as the team’s resident G.L., But he made some changes.

In the comics, Stewart was an architect and far more pacifistic than Hal Jordan, an Air Force guy. Timm made Stewart a grizzled veteran of the U.S. Marines. One with heavy combat experience. And not long after, that aspect became canon in the comics as well.

Mark Hamill’s Trickster Was Designed to Look Like Him in the Animated Series
Warner Bros. Animation

Mark Hamill was already a part of the DCAU, thanks to his iconic turn as the Joker. Although he appeared twice on Justice League, the producers found another role for him later on in the series, as Flash villain the Trickster. This was an Easter egg for longtime fans because Hamill famously played the character in live-action on the 1990s series The Flash.

But not only did Hamill voice the JLU’s version of Trickster, but the animators also seemingly designed him to look like Hamill too. It was the ultimate homage and one of our favorite animated Justice League facts.

The Justice League and Teen Titans Connections
Warner Bros. Animation

Although the Cartoon Network series Teen Titans debuted less than two years after Justice League and even shared key creative staff, the two shows are not in continuity with each other. More than one creative behind Teen Titans has admitted as much. At least, they’re not in the same universe on paper. The entire main cast of Teen Titans did appear as the Royal Flush Gang in the season two episode “Wild Cards.” But that’s more of a hat tip.

There are several Easter eggs tying both series together, however. Michael Rosenbaum voiced the Flash on Justice League, as well as Kid Flash on Teen Titans. Both versions are the Wally West iteration of the character, at different ages. The Titans’ archer Speedy appears on JLU, looking older but wearing his Titans uniform. And once again, voiced by the same actor. The only thing that glaringly keeps Teen Titans out of DCAU continuity is the fact that Robin is so young. Unless Teen Titans is a prequel to Batman:TAS? Probably not, but if that’s your personal headcanon, then who are we to argue?

Here’s to More Justice League Fun Facts in the Future
Warner Bros. Animation

And those are the tip of the iceberg. There are a lot more Justice League fun facts you might not know. Things like the JLU episode “ Epilogue” originally meant to tie up the entire DC Animated Universe, only for the show to get another full season anyway. Or that they originally pitched a more kid-friendly version to Kid’s WB, with teen versions of Flash and Steel. Luckily, Cartoon Network did not require kid sidekicks.

Justice League remains quintessential DC Comics on-screen storytelling, even fifteen years since it went off the air. Fans continue to maintain hope that HBO Max revives the series, similar to how Disney+ is bringing back the original X-Men. The current Justice League Infinity series from DC is a continuation of the animated show, so here’s hoping it’s a prelude to bigger things to come.