When it came to preparing for 2000’s X-Men, the first in what has stretched out into a now seven-movie series, director Bryan Singer avoided drowning himself in 40 years of comic-book history by binge-watching all 76 episodes of X-Men: The Animated Series. It was a logical move: The show, which premiered in the fall of 1992, did everything Singer’s film franchise would go on to do, spinning original stories out of the comic’s vast, established mythology and occasionally adapting the book’s legendary arcs as keystones for the series. After 14 years of grappling with Stan Lee’s crime-fighting mutants, the X-Men movie franchise finally takes the same approach by lifting directly from time-honored source material: Chris Claremont and John Byrne’s “Days of Future Past.” This past weekend’s blockbuster movie version is a story of apocalyptic visions and mass death that X-Men: The Animated Series managed to pull off in its first season.

“X-Men was a preexisting property and had taken those risks before,” says Julia Lewald, writer of X-Men: The Animated Series’ “Days of Future Past (Part 1).” “With that, the animated series was able to tell those stories because they were part of the X-Men world. I don’t know if any new property could have been created that told these stories in the way the X-Men were able to. Again, there was no talking down to the audience. There was no ‘They won’t understand this,’ no recapping it. Kids got exposed to a lot of important ideas that are paying off now.”

X-Men: The Animated Series debuted as part of Fox’s Kids’ third wave of Saturday-morning programming, alongside the more expensive and expansive Batman: The Animated Series. Today Batman’s creators are Comic-Con celebrities, while the passionate X-Men team remains prolific yet relatively anonymous. After a 1989 pilot for Pryde of the X-Men nearly killed the property’s’ chances at life beyond the comics (executives didn’t like Australian-accented Wolverine and cute dragon sidekicks, apparently), Fox Kids vice-chairman Margaret Loesch and executive Sidney Iwanter bargained, with promises of big ratings for a second incarnation. They hired Eric Lewald, whose credits included Chip & Dale’s Rescue Rangers, TaleSpin, and the cartoon Beetlejuice, as executive story producer — the animation world’s equivalent of showrunner. Working with soon-to-be Marvel editor-in-chief Bob Harras, Lewald filled out his staff with attentive geeks like storyboard artists/producers Will Meugniot and Larry Houston, and veteran animation writers, including his wife Julia.

Everyone from Loesch down to the writers knew X-Men: The Animated Series, much like Batman, needed to take its characters seriously despite varying tones (according to Eric Lewald, Iwanter would often refer to Batman as “cool jazz” and X-Men as “hard rock”). Early in development, Stan Lee expressed interests in running the show, though he envisioned something close to the original teenage vibe he introduced in the ‘60s. That didn’t work for Loesch, Iwanter, and Lewald. The Animated Series needed to aim for the intensity of the ‘70s comics, the era when Lee was long gone from the series and writer Len Wein first introduced Wolverine. So Lewald and his team crafted a first season that culled from the book’s darker themes. Colorful animation and broad dynamics would create a foundation for young viewers. Meugniot and Houston anchored it down with comic-book details.

“There were rumblings of ‘This could really flop,’” says Eric Lewald “[Executives would say,] ‘The scripts aren’t funny.’ ‘These scripts seem a little dark.’ ‘Gosh, I’m afraid this is going to be a disaster.’ There was serious anxiety until the first screening. But from that day onward, no anxiety.”

“Days of Future Past (Part 1)” and “(Part 2)” offer a microcosmic glimpse into the balancing act that X-Men: The Animated Series’ was able to pull off during its run. During the planning phases of season one, Marvel’s input steered which characters would wind up in the core X-Men group. There were obvious choices — Professor X, Wolverine, Cyclops, Jean Grey — and now-notable characters that Marvel hoped to leverage with spotlight positions in the series. Despite being a huge part of the comic books, the producers ditched Kitty Pryde in favor of the fresh-faced Jubilee for their spunky teenager role. Marvel also wanted Gambit, who had only been introduced in 1990 (safe to bet Channing Tatum was a fan of X-Men: The Animated Series). Characters who eventually grew into ensemble staples were marginalized at first. Eric Lewald says he pushed to have one of his favorites appear in season one.

“[Marvel] didn’t vote for Beast. Beast wasn’t part of the main team to start out the series. I, and the writers, liked him so much, we put him in and we got him arrested so he’s off to the side. The more we wrote, the more we wanted to go back to Beast. After the first 13, there was an agreement.” By the end of season one, Beast was freed from both literal and figurative jail.

The need to balance the potential of X-Men’s vast universe with narrative priorities came up again when Julia Lewald prepared to adapt “Days of Future Past” with “(Part 2)” co-writers Robert Skir and Martin Isenberg. Like Singer’s big screen version, the Lewalds grafted Claremont and Byrne’s framework to the available characters while seizing the opportunity of a future setting to incorporate studio requests. “Days of Future Past (Part 1)” picks up in the year 2055, with mutant-hunting Sentinel robots incarcerating the powered population in internment camps (or what Eric Lewald calls “the most intense realization of the series”). X-Men: Days of Future Past is equally dystopic, mirroring its animated counterpart with scenes of mutants marching enchained.

But where Singer’s version puts franchise star Hugh Jackman’s Wolverine front and center in a time-traveling journey, X-Men: The Animated Series went a different route. Wolverine in 2055 is still around and kicking, but he teams up with the brazen warrior Bishop, who leaps back in time to undo the horrific events of the present. As far as network notes go, the inclusion of Bishop as the twofer’s leading man was all the right kinds of positive. Julia Lewald says Fox Kids pushed to introduce a strong character of color. “They were very conscious of making the show inclusive without being intrusive about it. Bishop was that.”

The plotting of an animated show works differently from a traditional drama, with individual episodes farmed out to individual writers instead of being developed in a shared “writer’s room” environment. But Eric Lewald says X-Men: The Animated Series was the rare job where he could conceive arcs, bounce ideas of individual writers, take those back to Marvel, and piece together a serialized show that felt like a comic book. Sentinels became the focus of season one because that allowed Lewald to put crosshairs on the X-Men. In the pilot episode, the shape-shifting mutant Morph is killed by one of the towering robots. When the audience sees Cyclops, Storm, and Jean Grey’s tombstones, the deaths have impact.

The robots’ destructive power also made it easy for X-Men: The Animated Series to sidestep broadcast censors. “Thank God for Sentinels, in terms of action, what action we can have,” Julia Lewald says. “If action’s going to be big, it’s going to involve Sentinels getting bits torn off and thrown about. You couldn’t do that with living things on the shows.” There were times when the networked tugged on the show’s reigns; When the writing process found itself rubbing shoulders with the L.A. riots, Fox made requests to scale back any script containing city-in-flames set pieces (despite the animation process taking nine months). Eric Lewald adds, “The rules for Saturday morning are so restrictive that to make something intense, with a lot at stake, and people who really wanted to slaughter each other … it was a real balancing act.”

“Days of Future Past (Part 2)” has the luxury of throwing everything and everyone into the mix in a way that Singer’s smaller-scoped version can’t due to its function more as a sequel to First Class. In the culminating episode, X-Men political adversary Senator Kelly is revealed to be the target of assassination by Mystique (all true to the comics), revealed to be posing as Gambit. This leads to sizable throwdown across Washington, D.C., the X-Men going head-to-head with Mystique’s newly recruited Brotherhood of Mutants (including the Blob, Pyro, and Toad). Aside from Kelly being a non-factor in Singer’s adaptation — a character used up in the first two installments of the franchise — there’s a distinct gender divide between the cartoon and the movie. Jubilee flares up, Storm shoots gusts of wind at Pyro’s fireballs, and Rogue and Jean Grey combine powers to save a little girl from a falling cathedral.

Eric Lewald takes pride in his ass-kicking women of X-Men: The Animated Series and the number of female writers he had on the show. “We always get crap out here when we’re doing shows, ‘This is for boys. Don’t have any girl characters,’” he says. “Margaret was probably the main reason. It was her show. Storm and Rogue’s toys didn’t sell as well. [Usually] they would tell you no matter how good Storm is in the episode, the toys will sell half as many as the male characters. But it was a time when there were no toys selling well for Marvel. We didn’t have the pressure from the toy companies.”

“Days of Future Past” would be the first of the many condensed adaptations the show aired before ending in 1997. It even did the “Phoenix Saga,” which was bungled on the big screen in X-Men: The Last Stand. The ending of the series is fuzzy — Eric Lewald recalls writing an end-of-series five-parter, rounding out the run at 65 episodes, only to have Fox order additional scripts. With a number of companies involved, including Fox, Marvel, and Japanese importer Saban, the responsibility for who pulled the plug and why remains hazy — even for the creators. But the show’s legacy lingered; When it came time to develop the first X-Men movie script, 20th Century Fox brought on Eric Lewald and Will Meugniot as consultants. Not only did X-Men change the way networks viewed Saturday morning cartoons, it proved that large audiences were hungry for comic-book adventures in every medium. “The many X-Men movies have carved out their own place in the film world,” says Lewald. “We believe that the filmmakers have chosen, in their casting and storytelling general attitude, to usually follow our ‘serious’ lead. No winking at the camera, no ‘writing down’ to a comic-book audience.”