Tony Stark was marked for death more than four years ago. From there, it was just a matter of how to do it. The why had already been decided.

Almost everything else about the Avengers films Infinity War and Endgame changed over and over again. Superheroes beating up themselves in a mirror world. Smart Hulk appearing one movie early. Before this played out onscreen, it appeared first on a magnetic whiteboard covered in scrap paper, colored notecards, and one-of-a-kind superhero trading cards that were marked with ascending dollar sign levels—to keep salary costs in mind.

That conference room at Marvel Studios was where screenwriters Christopher Markus and Stephen McFeely were mapping out the two-part Avengers finale that brought closure to the multibillion-dollar Marvel Cinematic Universe and became two of the highest-grossing movies of all time.

Their whiteboard was one of the most closely guarded secrets in the world. Even the actors didn’t know all the details during shooting.

What fans still don’t know, even today, are the alternate versions—the diversions and dead ends, the reshoots and the reasoning that went into concluding the story lines (and sometimes the lives) of some of the most beloved characters on the planet.

While criticism from Martin Scorsese and other filmmakers has sparked debate about whether superhero films qualify as cinema, the screenwriters described a creative process aimed at uncovering surprises, heart, irony, and emotion that they hoped would resonate for moviegoers the way pop classics have for past generations.

At a Q&A at the Writers Guild of America West, Markus and McFeely told Vanity Fair how it all played out.

The Story Begins...

Anthony Breznican: You both wrote not only on Infinity War and Endgame, but all the Captain America movies—The First Avenger, The Winter Soldier, and Civil War—as well as Thor: The Dark World and Agent Carter. When you’re writing these other movies, are you also creating long-term plans for where you’re going years ahead of time? When would you say you truly began to consider what the final Avengers stories would be?

Christopher Markus: At the very end of [2011’s] The First Avenger, when Steve misses the dance with Peggy, you start going, I wonder if there’s going to be a way to get those two together...even though 70 years has passed.

Stephen McFeely: But we have not been writing the movie for 10 years. We only wrote for four years.

Markus: I mean, we didn’t start formulating Endgame until we got the job, of course. Otherwise we’d be insane.

McFeely: No, the guild doesn’t let you write for free. When Civil War came out, we’d already finished the first draft of both Infinity War and Endgame. We got the job as we were prepping Civil War. So that meant that Kevin Feige, the head of Marvel, had hired me, Chris, and [directors] Joe and Anthony Russo simply based on The Winter Soldier, to do both the Avengers movies.

Markus: ...And lots of sitting in a room planning Civil War. We nearly had a nervous breakdown.

McFeely: I bring it up because it’s such a leap faith, right? We’d only had one movie as a foursome under our belt. We got the job, thought about it all throughout the shooting of Civil War. And then the last four months of 2015, we cracked both those [Avengers] movies. So Tony’s death and Cap’s dance were on three-by-five cards in September of 2015.

There’s a debate about whether Marvel’s movies take enough chances and have enough surprises.

McFeely: Whether you like all of the 24 movies or not, the capital that Marvel built up allowed them to do things like make a movie starring a raccoon and a tree, right? You would’ve already had Iron Man 4 if it was any other studio. But they decided, No, we’re going to take chances on all these other things. To put a flag in the ground and say, We’re going to end something and take characters off the table, is, I think, kind of daring, but selfishly it was really great for us.

Why Tony Stark Had to Die

Why do you think it’s important that the story ends? Why is it important that Tony Stark ends? Why is it important that Cap gets to go back and have that dance and live a full life?

Markus: Because it legitimizes the whole thing. If you just keep going until it peters out or you lose interest, it kind of decays backwards, making [people] think less of everything that came before. To have the opportunity to very deliberately tie all those threads together and have it add up to something and have it end, that’s what stories are about. That’s how you judge whether something was great or not. If at the end of The Great Gatsby, they got into a car and drove off and then we wondered what was going to happen next? We wouldn’t have remembered that.

The Greater Gatsby, The Greatest Gatsby…

McFeely: More Great Gatsby, Not-So-Great Gatsby...

2 Great 2 Gatsby.

Markus: It needs an end or it loses meaning. The end is what cements the thing, to actually sew it together and bring it to a crescendo, and yeah, take people off the board, finish their arcs. If Tony made it out the other side, and Iron Man 4 was waiting there, you’d be like, [shakes head] One too many...

But why does he have to actually die in order for that to happen? You could have given him a conclusion that still had him survive. Others got that.

Markus: Because, really, the man is very determined. He would keep going.

McFeely: We realized over the course of the movies that Cap and Tony were on crossing arcs. Cap, who had started as completely selfless and was jumping on grenades willy-nilly, was becoming more self-interested. Not to say selfish, but if you watch Civil War, particularly, he’s making decisions based on what he wants, even if it breaks up the Avengers. And Tony started as the brash billionaire playboy, and the stakes are growing for him, the responsibility’s growing for him. We realized at one point, late in 2015, that for Steve to be his best self, he was going to have to get a life, and for Tony to be his best self, he might have to lose his.

Sometimes the grenade goes off, right?

McFeely: Sometimes the grenade goes off.

Markus: And that’s why [Captain America] can’t die in this movie, because he was willing to die in the first one. That’s not a journey.

In the Secret Writing Room

What’s it physically like to write one of these movies? Where do you begin breaking the plot? Do you do that together? Are you doing that in a room with Kevin Feige? Are you doing that with the Russo brothers or the broader Marvel brain trust?

Markus: A conference room is reserved and the first day is the best that will ever smell. Basically we’re there every day, banging away at the story. People come in as they’re available. Joe and Anthony were in post on Civil War for a lot of the initial plotting. They’d come in and go, “That’s insane!” And Kevin is a very busy man, so you get him when you get him. But we were in there every day, Steve with his stack of three-by-five cards, not just plotting out two movies—but multiple versions of two movies, taking them down the road and going, “You know, this movie we’re plotting out doesn’t work. Let’s take those characters down.” It takes months if you’re lucky.

McFeely: On one wall is Movie One, and one wall is Movie Two, and the third wall has baseball cards of all the Marvel characters, and we could move them around…

Are they actual collectible cards?

McFeely: They’re all in my dresser. I think I’ll hold on to them for a while.

I mean, are they specially made for this? One of a kinds? Or the kind anyone could buy commercially?

McFeely: Marvel makes them. Yeah. Some intern in-house makes them. They have a magnet on the back. They get dog-eared and bent and stuff. [Each one] says if we have them or not for this movie. And there was a little rating. We didn’t know how much [money] each actor made, but it had either one dollar sign or up to five dollar signs.

So you would keep in mind how much they cost to be in the movie?

McFeely: It was sort of just a guideline.

Markus: They would allow us to do anything in anybody’s contract. We’d get to renegotiate it as needed, but it was a fascinating glimpse into the other side.

Was Marvel ever like, “There are too many dollar signs in this scene?”

Markus: No, it was, “You better damn well have a good story for us!”

McFeely: You actually try not to leave the five-dollar-signs on the sidelines.

So you’re popping those cards on there, drawing a timeline for the story. How does it look?

McFeely: In the beginning stages it’s a, Oh, wouldn’t it be interesting if Groot and Rocket and Thor went on a journey together? What kind of chemistry could you get from that? But also, we took this job because it scared the hell out of us, because that first movie has 23 [main] characters in it.

First movie meaning Infinity War?

McFeely: If you know that movie, and you know how we ended it, it was in large part just so the second movie would have fewer characters. And we could work with that! [Laughs] We started with 65 characters. I mean, it’s just everyone who was vaguely alive. And when we narrowed it down, you don’t want 23 people in a scene—ever. So that’s what the cards were for, to sort of—

Visualize it?

McFeely: Well, pick dodgeball teams, right? “All right, that’s going to be a team, and we’re going to tell four small stories.” Infinity War was very simple. It feels complicated simply because things are being woven together, but the stories themselves are really easy.

Markus: I don’t think standing in the middle of a star, holding it open to allow the energy to pass through, which melts steel, to create a magic axe…I don’t think there is anything easy about that. [Laughs.]

Saving Black Widow—Then Not

We talked about Cap and Iron Man, but the other big sacrifice in this movie is Black Widow. How did you decide her life had to come to an end?

McFeely: Not without some controversy. We certainly thought long and hard about it. We knew we were killing the first female hero of the Marvel Universe. We stupidly came up with these rules in the first movie—someone’s going over that cliff. So we had to decide. By the way, you had to easily love the person next to you, so we couldn’t send Steve Rogers and Hulk. So it's a puzzle of our own making, but it felt like it was the resolution of her arc, that if she could sacrifice herself for her new family and for half the universe, that was worth it to her.

There was an alternate sequence shot in which Hawkeye is the sacrifice instead. Did you test both on fans?

McFeely: A number of women on the crew, when we said, “Hey, we’re thinking maybe Hawkeye goes over,” said, “Don’t you do that! Don’t rob her of this!” And then it choked me up because I think we would have a much different conversation if Hawkeye had pushed her aside.

It gives her the chance to jump on the grenade?

McFeely: She jumps on the grenade. I’m really proud of that moment. I don’t have any regrets. The only regret is that it comes at the end of Act Two. So you can’t really roll around in the grief because we’ve got another hour of movie and we haven’t solved the A-plot problem. So that’s the downside.

Professor Hulk’s Tenure Denied

What can you share about those alternate versions, the dead ends or ideas that you thought maybe were cool but just didn’t work for the story?

Markus: The alternate versions were sort of side roads we served for characters who had left the plot behind. It would be entertaining and it would be interesting and it would be cool to look at, but it would cause you to pause on the Thanos plot, and suck the air out of it. There was a sequence in the first movie where they went into the places in the Doctor Strange universe called the Mindscape and everyone faces themselves. It was great but had absolutely nothing to do with anything.

Faced themselves as in battled themselves?

McFeely: Banner meets the Hulk, I think in the arena from Ragnarok. Only one of them was getting out of there, and then that one showed up in Wakanda [in Infinity War] and he had merged. That merging that currently happens in [Endgame] in a diner, and he’s eating a huge stack of pancakes? That initially happened at the end of Infinity War.

How did that alternate version play out?

McFeely: The Hulk refuses to come out, if you remember, and [in the discarded story line] they eventually came to a realization or a compromise and he busted out of the Iron Man suit and beats the heck out of this [monster]. That whole third act is a march toward losing, and this Hulk scene is a big win, right? It’s a guy solving his problem and being a funny character because now he’s eloquent. We had to, at the last second, scrap all that, put aside all these scenes that used to have Smart Hulk, and then reshoot the first act of Endgame, going to Thanos’s country lodge, that used to have the Smart Hulk.

Markus: We made Mark Ruffalo gain over 500 pounds… [Laughs.]

This actually solves a mystery for me, because when I was on the set of Infinity War, I watched Mark playing the Hulk in the Wakanda battle. After that didn’t happen in Infinity War, I assumed, They must be saving this for the second one. But you actually reshot and removed that story line?

McFeely: We had to change it.

Markus: We wanted everybody to have this enormous journey in the five-year jump [after the Thanos snap], and to really see, in sometimes shocking ways, how the loss had affected them. We hadn’t given Banner [a change] because we had transformed him earlier, and he had nowhere to go. And suddenly by needing to take it out of the first movie, it was the perfect thing.

Why Thor and Hawkeye Had to Live

We see Thor go through a big physical and emotional change in Endgame. You noted Marvel decided not to do Iron Man 4, but Thor’s going to be the first Marvel character to get a fourth solo film [2021’s Thor: Love and Thunder].

Markus: You didn’t see that coming, did you?

McFeely: Right. Well that’s a crazy journey for character and actor. After Thor: The Dark World, no one is saying, “Thor is my favorite character,” but thanks to [Ragnarok director] Taika Waititi and Chris Hemsworth’s willingness to be a goofball, I can’t think of a better three-movie run for an actor to steal the show, from Ragnarok to Infinity War and Endgame. That scene in Infinity War where he tears up, talking to Rocket about all the things he’s lost, is hilarious and sad. And I remember on set that day, watching this guy just crush this scene. I mean, I was angry. He’s just so handsome and now he can do this.

We see the story essentially end for Tony, for Steve Rogers, for Natasha, even for Hulk and Bruce...

McFeely: [Nods] The O.G. Avengers, we put them down. It escorted them off the stage or gave them some sort of conclusion to settle their emotional issues. Nobody becomes a superhero because they’re really well adjusted; they do it because they’re screwed up on some level. [By the end of Endgame] everybody is kind of fixed, or dead.

But Clint Barton and Thor, they’re continuing on, they have other stories. Hawkeye is getting a Disney+ series.

McFeely: We could have had a bloodbath and all six of them gone down swinging, but that seemed even more depressing.

But why those two? Why did others have to end, but Marvel felt these two had potential to keep going?

Markus: It’s not necessarily that we knew they’d get more stories, it’s just that…Thor has sacrificed and sacrificed and lost and lost. It’s not a good ending to kill him. To have him finally, reasonably content with himself—and with his current weight, by the way…

...Is more satisfying?

Markus: There were some people who were like, “No, he has to magically lose weight.” [Laughs.] That was one of those sobering moments on set where some people were afraid, He’s going to put on the fat suit, and he comes out and basically looks like everybody on the crew. That’s not a fat suit! That’s a normal-person suit! But Thor was resolved. There’s a joy in letting him go off aimlessly into the ends of the universe. And Clint got his family back, and that’s something. That’s the whole reason he was doing it.

There were so many questions about the timeline and where Captain America lives with Peggy Carter, whether that’s an alternate timeline, whether he’s in our timeline. Is it good that people are still asking that, or do you feel like audiences are missing the obvious?

McFeely: Oh, it’s great!

Markus: Yeah, that’s fine. Those are unsatisfied questions. Those are intrigued questions. I’m delighted at people still chewing over this thing. You know, if it’s, That’s stupid and I don’t like it and I’m talking about it because it was dumb, that’s one thing. But if it’s, I honestly don’t know, and it’s kind of cool to think about, that’s great.