When the producers of The CW's superhero dramas announced a four-part crossover, most fans likely didn't expect Arrow, The Flash, Supergirl and the Legends of Tomorrow to unite against the threat of alien invasion -- let alone one inspired by a 1980s DC Comics miniseries. But then in July. "Arrow" Executive Producer Marc Guggenheim revealed the story does indeed draw inspiration from "Invasion!," with the alien Dominators serving as the primary villains.

But the four-way team-up doesn't merely give a nod to its comic book roots, Guggenheim now assures. “I will say that their goal is very closely related to what was established in the comics, and it does have to do with metahumans,” he tells Entertainment Weekly. “It’s very, very faithful to the comics.”

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In "Invasion!," the gene-manipulating aliens the Dominators assemble a coalition of extraterrestrial races to invade Earth, with the apparent goal of eliminating the threat posed by “metahumans” — that is, super-powered people. Unknown to the other members of the alien alliance, however, the Dominators intend to harness the metagene and create their own army of metahumans.

Calling it "the most ambitious crossover we’ve ever done," Guggenheim describes the event as "one big epic movie of a story."

Viewers are by now accustomed to characters from one Arrowverse series appearing on another, whether it's "The Flash's" Barry Allen visiting the world of "Supergirl" or "Arrow's" Ray Palmer and Sara Lance joining "The Flash's" Captain Cold and Heat Wave (among others) on "DC's Legends of Tomorrow." However, Guggenheim stresses we've never seen anything of this scale.

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"It’s not setting up any other spinoffs, it’s just big, bombastic, huge action," he says. "There’s also some really poignant character moments. There’s a lot of plot lines, particularly I would say in 'Flash' and 'Legends,' that come to fruition in the crossover. It’s by far the most ambitious thing we’ve ever attempted. I want to say it’s by far one of the most ambitious things anyone in network television has ever attempted. It’s completely insane.”

The sprawling "Arrow"-"Flash"-"Supergirl"-"Legends of Tomorrow" crossover is expected to debut in November on The CW. "Supergirl" airs on Mondays at 8 p.m. ET/PT, "The Flash" on Tuesdays at 8 p.m. ET/PT, "Arrow" on Wednesdays at 8 p.m. ET/PT, and "DC's Legends of Tomorrow" on Thursdays at 8 p.m. ET/PT.