Marvel Studios is known for its secrecy — both among fans, and the stars of the movies themselves.

Take Sebastian Stan, for instance. He landed the crucial role of Bucky Barnes, the best friend of Steve Rogers, in 2011’s first “Captain America” film.

The movie ended with Bucky presumed dead, but with the actor signed to a nine-picture deal and the comics providing plenty of roadmaps for the character’s future, it was pretty obvious to everyone that his fall in “The First Avenger” would not be the last we heard from Stan or his character.

Common wisdom aside, however, no one knew exactly how Barnes would return — include Stan himself.

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“I knew about the storyline of the character, and kind of what happens in the comic books … but everything was sort of ‘Knock on wood, if things go well, we’ll see how it goes,'” Stan told TheWrap, referring to the uncertainty surrounding the future of his big screen alter-ego.

As it turns out, the actor found out that Barnes would come back as the villainous Winter Soldier — an amnesiac Soviet assassin — “about two years after we shot the first film,” he said.

So Stan did some recon work himself, working off clues he found both in the comics and in the initial script for the first film. He also did his best not to worry about how the other Marvel films would or could impact his own — even if it boasted crossover stars like Scarlett Johansson (Black Widow), Samuel L. Jackson (Nick Fury) and Cobie Smulders (Maria Hill).

He was just excited to be working with them, he said, and got himself ready to go when the call came.

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“When you have a lineage of books to turn to, you can kind of find cool character stuff that you hope to kind of bring into the movie if there’s an opportunity,” Stan said.

“Some things just don’t translate very well from the page to the screen,” Stan continued. “And sometimes they need to be kind of revised a little bit, just to make more sense, so that’s why, at least in this case, Bucky Barnes from the beginning of the movies was never that teenage sidekick that you saw in the comic books … They really wanted it to have a different dynamic and friendship.”

Also helpful: Talking with the person that created the character of The Winter Soldier in the first place.

“I had spent some time talking to [“Captain America” comics writer] Ed Brubaker and kind of getting some ideas as to where he got some of his inspiration for reviving Bucky,” Stan explained. “He talked a lot about the Cold War and the KGB and all the spy movies that he really enjoyed in the 60s and 70s. And that led me to go to sort of watch those movies and doing research on that stuff and fall in love with that idea a little bit.”

He added: “You never know if one day they decide to do it a certain way and take the story a certain way or not, so if they do, you want to cover yourself.”

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Of course, Marvel films are far more than character studies (or, in this case, political thrillers). They’re also filled with action, and Stan’s Winter Soldier in particular is a sort of human weapon.

Chris Evans‘ jacked physique has long been the subject of conversation around the “Captain America” movies — his costume does little to discourage that. But Stan also had to put in months of training, on top of working around CG and with the complicated mechanics of technical effects — “Cap 2” has more on-set practical effects than any other Marvel film.

“There’s a whole thing about it where you’re like, a little kid, because you actually just have to remember that Cowboys vs. Indians game you played when you were little, and there was something about just being imaginative to go there and allow yourself to go there,” Stan explained, regarding working with green screen and getting into a fighting mindset.

He went on to say: “I gained a new appreciation for a lot of these actors who do a lot of action movies. There’s a reason why Tom Cruise is good at what he does in every movie and why he does his own stunts… It’s not the easiest thing, to kind of pick up a gun and shoot and look cool and not blink because you’re firing these loud noises, it’s a whole art in itself.”

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Now that the film — which is tracking for a $90 million debut at the US box office — is complete, Stan is finishing up his promotional duties (which included ringing the bell to open the New York Stock Exchange and entering a London premiere to people chanting “Winter! Winter!”). As a result of the promo tour winding down, Stan is sort of in a holding pattern to see where his character will end up next.

One thing he knows for sure: He’s not in the next film, “Avengers: Age of Ultron,” which is just beginning production.

“I’m not involved in that; I think that they’ve got their hands full over there,” Stan said, laughing. “They’ve got quite a number of characters already. It’s one of those things where it’s nice to know that the opportunity’s out there on the table to work with these guys in the future. That in itself is very gratifying, and after that, I don’t know. I don’t really ask questions, I just, like I said, when they decide they want to use me, they know they can, and I’ll be there… I can continue to kind of go on with life, and then when a nice phone call comes in about going to work again, then it’s a great surprise and a good feeling.”

“Captain America: The Winter Soldier” hits theaters April 4.