What Could 'Phase Zero' Mean for Avengers: Doomsday? My Theory on the Russos' Big Idea

The Russo brothers and Robert Downey Jr. said a lot about Avengers: Doomsday in a series of interviews at South by Southwest, including the idea that they were going back to "phase zero" of the MCU. I had my share of gripes that day, but I have to admit those interviews do shed a lot of light on their exact plan for this movie, and I think they were trying to communicate a secret message about who Downey's Doctor Doom really is.

These are details that no one else seemed to be picking up on, so I'm going to lay out what was said, and then what I think phase zero actually means.

The AGBO coffee popup was mostly influencers, and it hid Doctor Doom origin clues

The day started with the Russo brothers appearing at a popup coffee shop that AGBO put on in London. While this was presented as a fan meetup, I can confirm through some forensic visual investigation that most of the people the Russos posed for pictures with were actually influencers with major followings. I've attended events like this, and I get the game. I just have some mixed feelings about the way they teased it on social media beforehand, as if it was going to be something all Marvel fans everywhere could enjoy together.

Still, I previously broke down the surprising number of Doctor Doom origin clues spread throughout that popup, which I'm pretty sure are telling us Robert Downey Jr.'s Doctor Doom origin story in Avengers: Doomsday. I think they point to a pretty comic accurate Latverian origin, with his parents in Latveria and an enemy he had in Latveria. They may also answer why the Latverian delegation was absent in The Fantastic Four: First Steps.

We also realized there's a specific Latverian letter system at the popup. Some friends on Reddit decoded it for us, and it turned out not to be a 26 letter substitution code but rather what's called a phonetic language. But even after that goofy popup, these filmmakers were more open and transparent than they have ever been in the interviews that followed at the conference.

The Russos called Doctor Doom's costume their favorite of their five Marvel films

First, there was a panel with the Russo brothers and Donald Mustard, who now works with them as a partner at their production company AGBO, and who actually cameoed as a sorcerer in the Battle of Earth in Avengers: Endgame. The panel was moderated by a Variety editor at the Truman Brewery in East London. According to Variety, the two revealed that Robert Downey Jr.'s Doctor Doom costume is their favorite out of all five Marvel films they've directed.

When asked why, Joe Russo teased, "Y'all have to see." With the audience eager for more, Anthony Russo added that "It's representative of the character in a way that the costume and the character really, really fit."

Joe then explained that their challenge has always been balancing what they love from the comics with what other fans love, and adding something original to the storytelling. "We're never translating directly from the comics, we're always adding a new experience that hasn't been written yet in terms of who these characters can be," he said. He added: "Doom hits that sweet spot between being very specific and unique to the original story that happens within this film, but also delivering on what the most awesome things are about Doom in the comics." I found that interesting, and it comes back into play in my theory below.

Stephen McFeely's idea "broke the skies open" for Doomsday

A reporter from The Hollywood Reporter was also in attendance and reported additional quotes from this panel. According to that report, Anthony Russo said that even though there was a strong sense of closure after Endgame, and the brothers were admittedly exhausted after seven years leading the franchise, it was an idea from writer Stephen McFeely that reignited their desire to return to the MCU.

"He came up with this creative idea that reignited the project and I can't talk about that creative idea because it's the basis for Doomsday, but that idea all of a sudden broke the skies open for us and we saw all new kinds of possibilities with that idea," Anthony said. Broke the skies open kind of sounds like an incursion to me.

Joe Russo said Doomsday is back to phase zero of the MCU

According to The Hollywood Reporter, Joe Russo said they're "Back to phase zero of the MCU with Doomsday and Robert Downey Jr. playing antagonist Doctor Doom." The reported quotes went on to describe a series that keeps shifting, changing, surprising you and reinventing itself, with the promise that "you're going to see some shifting and changing with Doomsday."

The brothers also said they had been with Robert Downey Jr. earlier that day, and that they had both been talking about this concept of being back to phase zero. "This is starting over from scratch. We want to make sure everybody feels like this isn't leaning on anything from the past."

On juggling a huge cast, Joe said that each one of those actors is playing somebody's favorite character, so if you don't serve that character properly, you're going to disappoint someone in the audience. He said they grew up in the biggest Italian family and understand how to tell stories with multiple characters, which comes down to very subtle point of view shifts. His example: "If Thor, when he lands, actually cuts off Thanos's head, then Thor becomes the hero of that movie."

Robert Downey Jr. said they're "zeroing out the board"

Later that evening, the Russo brothers appeared on stage after a screening of Avengers: Infinity War with Anthony Mackie, Winston Duke, and surprise guest Robert Downey Jr. When Downey entered the room, the whole crowd roared. It was the same roar I heard at CinemaCon and in Hall H when Downey was announced as Doctor Doom in July 2024. It's really why Marvel Studios feels so confident about Doomsday.

But Downey's exchange with the Russos didn't come across as overconfident. It showed some humility. After a jokey exchange with Joe Russo about Doctor Doom and Thanos, he talked about how impossible it would be to top Infinity War and Endgame: "We can't beat it. We can't stand on the shoulders of these giants of Infinity War and Endgame. So, we're literally zeroing out the board and we're going to try to earn your trust and respect all over again. And with the likes of these fellows, I think we got a pretty good shot."

I know Downey was really referring to the long gap since Endgame and the fatigue all of us have felt since 2019, and to how he had to earn that trust as Iron Man back in 2008. He probably didn't mean what I'm about to say, but he did say it while sitting next to Anthony Mackie, whose 2025 film Captain America: Brave New World kind of underperformed, did not exactly carry the torch the way Marvel Studios hoped, and was seen by some critics as part of that era of franchise fatigue. I think that's why Downey pivoted to that closing line, pointing to the other four guys on stage as the reason Doomsday has a good shot. And notice how he made a beeline to hug Anthony Mackie.

My theory: Doctor Doom is the default version of Downey's character

That phrase, zeroing out the board, does feel like a talking point Downey discussed with the Russos, matching their phase zero remarks. Starting over from scratch, earning your trust all over again. So what do they mean by that? And why can't they even speak abstractly about the big idea McFeely had in the middle of the night, which they have said in past interviews was the one idea that convinced them to come back?

In the past I speculated that this big idea was the consequences of Steve Rogers' decision to stay in the past with Peggy Carter, and how that might have caused an incursion that hurt Victor von Doom in some way. It's possible that's part of the plot, but based on what they're saying now, I don't know if that was the big idea. I think the big idea is their reason for casting Robert Downey Jr. as Doctor Doom.

I think their idea is that the main Marvel Universe, the Infinity Saga we watched, is the anomaly: the guy with this face ended up being Tony Stark in the 616 universe, but in all other universes, the guy who looks like that is Doctor Doom. I think Doctor Doom is the natural default state for someone who looks like Robert Downey Jr. in any Marvel movie universe. He's a genius billionaire playboy philanthropist, a doomsday minded futurist, someone who wants to put a suit of armor around the world, but normally he goes by Doctor Doom.

I think phase zero means a brand new Doctor Doom origin story

So when they say they're starting over from phase zero, I think they're talking about their excitement to tell an origin story from before the MCU as we knew it: the real story of this man, before we met him in this alternate universe as Tony Stark. In that telling, we should really know him as Victor von Doom, a Latverian scientist and sorcerer, the son of Cynthia and Werner, who went to college with Reed Richards and Ben Grimm, was ridiculed by them, went back to Latveria, took power and renamed Hasenstadt to Doomstadt, and then watched from the sidelines as Reed Richards doomed his world with some multiversal experimentation.

I think Downey, the Russos and McFeely are really excited to tell a new Marvel movie universe origin story, a phase zero story that won't even try to outdo Thanos in Infinity War and Endgame, but will start much smaller. In effect, it would make the legend of Tony Stark in the 616 universe feel all the more exceptional. It would also explain how they're keeping the comic accurate elements that make Doctor Doom unique while telling their own Doctor Doom story that isn't pulled exactly from the comics, just as Joe described.

What do you think phase zero for Doomsday means, and could this be the big idea from the Russos and McFeely?