Thanks to a Captain America: Civil War casting call that's looking for extras in Atlanta, we finally know just how the comic book Civil War has inspired the big-screen movie.

When Civil War #1 landed in readers' hands back in 2006, Marvel fans discovered the reasons that their favorite superheroes were about to go to war against one another: A little-known team of young adult heroes called the New Warriors was attempting to boost its fame by being filmed for a reality TV show, and they made a really bad call, resulting in an explosion that killed some 600 innocents in the surrounding area, including an elementary school where 60 children died. The public immediately demanded government regulation of the Avengers, X-Men, Fantastic Four and all the rest.

Superheroes would be trained and licensed to operate as government agents. Sounds reasonable, right? Iron Man saw the logic in it, and agreed to sign on to avoid another senseless massacre. The problem arose when Captain America learned that as a government operative, it would be part of his responsibility to hunt down and detain unlicensed heroes who refused to become government agents. In effect, if you have superpowers, all of your choices in life were revoked and you were required to work for the government. That didn't sit too well with freedom-loving Cap.

So how does that scenario translate to the Marvel Cinematic Universe? Not perfectly, that's for sure. The biggest problem: the comics universe is populated by literally thousands of superheroes, while the MCU has only a handful. How is Captain America: Civil War going to use the same ideas and themes but in a drastically different world? Here's the synopsis that went out with the casting call.

One only need watch the trailers for Avengers: Age of Ultron to see that it's a globe-trotting adventure that leaves plenty of death and destruction in its wake. Ultron himself is out to destroy humanity, after all, and he won't be much of a threat if he can't come awfully close to doing it. Hence, the movie will substitute the small-town USA massacre by pinning the whole thing on Ultron. Darn you, evil robot!

Captain America: Civil War will have all the governments of the world coming together in an unprecedented piece of collective legislation that requires global superhero regulation. In the comics, this U.S.-only legislation was executed by S.H.I.E.L.D., but that probably won't be the case in Captain America 3 since Cap's last movie dismantled S.H.I.E.L.D. entirely. (Well, almost.)

Logic demands that for Captain America: Civil War to depict a rift between superheroes, there need to be a large number of them in the movie for it to mean anything. We already know that the movie will star Chris Evans in the title role, Robert Downey Jr. as Iron Man, Scarlett Johansson as Black Widow and Jeremy Renner as Hawkeye. Beyond the Avengers, Anthony Mackie's Falcon will appear, as will Sebastian Stan as Bucky Barnes, aka the Winter Soldier. The movie is also expected to introduce Chadwick Boseman as Black Panther, and rumor has it that it could mark the debut of the new Spider-Man in the MCU as well. What about that new guy — Paul Rudd's Ant-Man? He'd have to register, too.

That's eight superheroes. A war of four-on-four, perhaps? But what about the other Avengers? For something this big, one would expect Thor and Hulk/Bruce Banner to weigh in — two heroes who would likely just laugh at the notion of being regulated by regular humans. And what of the new Avengers introduced in Ultron — Quicksilver, Scarlet Witch and Vision? Might any of them appear? If not, Marvel will need some really good explanations for their absences. Hopefully that doesn't include (gulp) their deaths. Bleeding Cool reported a rumor yesterday that all of the above do appear in Civil War, but a Marvel exec quickly shot that report down.

Regardless, with so many heroes onboard, maybe we should just call this one Avengers 2.5.

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