The incredible news that Robert Downey Jr. is in talks to bring Iron Man to Captain America 3 has set the Internet on fire, and with good reason, as the most likely story arc that Marvel will use in this casting scenario is Mark Millar's fabled Civil War limited series that ran from 2006-07. Nothing has been confirmed at this stage, but with the incessant rumors and leaks coming from people close to the project, it appears highly likely that Marvel will draw the basic storyline of Cap 3 from Civil War.

So what's the fuss about Civil War? Well, THR has put together five key things that occur in the comic series that could have heavy ramifications for Cap 3 as well the wider Marvel Cinematic Universe, future Ant-Man and Dr. Strange movies, and even planned Avengers sequels several years from now. Warning, major Civil War spoilers ahead. 

1. Civil War needs more than just Iron Man and Cap

Millar's Civil War featured a huge number of Marvel characters who were forced to take sides following the introduction of the Superhero Registration Act, an American government initiative to regulate and control vigilantes, who also must reveal their identities. In the comics, Luke Cage, Human Torch, Invisible Woman, Daredevil, Cable, Nick Fury and Captain America rebel against this government attempt to control superheroes. In favor of the legislation you have Iron Man, Ant-Man, Spider-Man, Black Widow, She-Hulk, Mr. Fantastic and many others.

2. Civil War features Ant-Man and Dr. Strange

Both characters play their parts, to varying degrees, in the series, and with both slated to have their own stand-alone features, it looks like a Civil War-based Cap 3 could very well be the setup for the third phase of the Marvel Cinematic Universe. So expect the consequences of this film to run on into future Avengers sequels too. 

3.Tony Stark is the villain

Iron Man lines up behind the government and is the chief advocate for the Superhero Registration Act; not only that, in Civil War, Stark doesn't seem all that concerned with locking up rebellious superheroes in inhuman conditions. Cap on the other hand feels the Act is dangerous government overreach and violates civil liberties. We're gonna have to face up to the fact that Stark will likely be the bad guy in any Civil War movie adaptation. However, the series also dealt with the moral ambiguity of the situation, with both Iron Man and Captain America coming at the issue with good intentions. 

4.Civil War is packed with superhero teams

There's the Avengers of course, as well as the New Avengers and the Mighty Avengers and not forgetting Cap's rebel alliance the Secret Avengers. Also making appearances are the villainous Thunderbolts, the Runaways, the Great Lakes Initiative, X-Factor and the X-Men. 

5. Civil War sees the death of Steve Rogers

Yep, it happens. There's no getting away from it, the end of Civil War sees Cap get assassinated. After the end of the war, Stark assumes control of SHIELD.