Marvel Studios just made its Avengers: Doomsday ensemble even bigger, confirming a 25th superhero actor for the cast. The studio first laid out the bulk of its lineup during a sprawling half-day livestream in Spring 2025, where director's chairs revealed the majority of the cast ahead of production. Additional names have been confirmed in the months since, including official word that Chris Evans would return as Steve Rogers. The newest addition, however, stayed under wraps until Marvel Studios took the Hall H stage at San Diego Comic-Con (SDCC).
When Marvel Studios first pulled back the curtain on Avengers: Doomsday's ensemble during that infamous livestream, Hayley Atwell's chair was nowhere to be found.
She was one of several major names held back from the initial cast reveal, alongside Chris Evans' Steve Rogers, likely holding out to make the impact of their return even greater. Reports had even linked Atwell to the project as far back as December 2024, but Marvel Studios never made it official.
That changed the moment she walked out on stage at SDCC, finally confirming what insiders had been saying for well over a year: Peggy Carter is back.
Really, the signs had been there for months, and most fans had already assumed she was in the movie. Evans' return as Steve was already confirmed in December 2025, when a teaser built entirely around the character first premiered during Avatar: Fire and Ash showings.
That footage showed Steve pulling up to the same house where he and Peggy shared their long-awaited dance at the end of Avengers: Endgame, folding away his Captain America uniform, and cradling a baby all but confirmed to be his and Peggy's child.
With that groundwork laid, Atwell's SDCC appearance did more than confirm her return... it hinted at the idea that Peggy won't just be a two-second cameo, but another genuine focal point of Doomsday.
Atwell isn't the only face rounding out this loaded cast. She's joining a wide range of MCU and 21st Century Fox X-Men alumni, all ready to take on Robert Downey Jr. as Doctor Doom on December 18.
All 25 Superheroes and Variants in Avengers 5: Doomsday
Steve Rogers
Steve's return seems triumphant in Doomsday, but comic fans know he hasn't always been one of the good guys. If Doomsday wants to lean into the multiverse's darkest corners, a glimpse of Captain Hydra would be a dark misdirection.
Thor
Chris Hemsworth's Thor is likely sticking to a single timeline this time. Between running into his lost brother Loki (Tom Hiddleston) and facing Doctor Doom axe-forward, the God of Thunder already has enough on his plate without running into another version of himself.
Mister Fantastic
Reed Richards (Pedro Pascal) might be the one character actually built for a multiversal crowd. The comics' Council of Reeds is a literal team made up of alternate-timeline Reeds, and Doomsday's colliding universes give Marvel Studios every excuse to let the smartest man alive meet a few of his equals.
Invisible Woman
Sue Storm (Vanessa Kirby) spent Fantastic Four: First Steps holding her family together (primarily on her own), and Doomsday looks content to let this one version of Sue keep doing exactly that, especially with Franklin in danger again.
Human Torch
Johnny Storm (Joseph Quinn) is still just getting started in this role after his Fantastic Four: First Steps debut. Hopefully, a certain arachnid character could swing by the superhero.
The Thing
Ebon Moss-Bachrach's Ben Grimm is about as singular as MCU characters come. There's something fitting about the team's most physically unique member staying a one-of-one instead of being duplicated across universes.
Ant-Man
Scott Lang (Paul Rudd) has seen the multiple versions of himself already up close and personal; fans should expect Ant-Man's story to focus on protecting his daughter, Cassie, again.
Yelena Belova
Yelena Belova (Florence Pugh) doesn't need an actual Variant to cause chaos. The Doomsday trailer already showed Mystique (Rebecca Romijn) borrowing her appearance entirely, which might be an even better trick than the real thing.
US Agent
Technically, John Walker (Wyatt Russell) has already played a Variant of sorts. The character spent an entire season of The Falcon and the Winter Soldier trying, and failing, to be a knockoff version of Captain America.
Captain America
The legacy of Captain America is spread across Avengers: Doomsday. Anthony Mackie's Sam Wilson probably won't have a Variant of himself appear, but fans hope he retains the mantle of Cap.
Shang-Chi
Between the Ten Rings and Doctor Doom's forces, Shang-Chi (Simu Liu) is one of the best-equipped Avengers. It would be a scary sight seeing an evil Variant of him going up against our heroes.
Cyclops
James Marsden slipping back into the visor after two decades away is the real headline here. No Variant necessary in Doomsday, but that doesn't mean a new take on the character could be introduced in Secret Wars.
Professor X
Here's the fun wrinkle: Patrick Stewart already played a Professor X Variant, and Doctor Strange in the Multiverse of Madness killed that version. Technically, Professor X has already been killed four different times on film.
Gambit
Channing Tatum barely got a full hand of cards to play during his Deadpool & Wolverine cameo. The hope for Doomsday isn't a new Variant so much as a fuller deal: some real answers about the mysterious universe this Gambit calls home.
Black Panther (Shuri)
Shuri (Letitia Wright) will be continuing her journey after defeating Tenoch Huerta's Namor in Wakanda Forever. Marvel Studios appears to be saving David Jonsson's debut as the grown T'Challa Jr. for Black Panther 3 (or maybe even Secret Wars) instead of folding him into the Doomsday ensemble.
Bucky Barnes
Just how big a part Bucky Barnes (Sebastian Stan) plays in Doomsday remains one of the murkier pieces of the whole puzzle. But his reunion with Steve is certainly something longtime MCU fans are looking forward to.
Ghost
Ava Starr (Hannah John-Kamen) has unfinished business with Scott Lang dating back to Ant-Man and the Wasp. They're shown in the same room in the first Doomsday trailer, so a few witty lines discussing their past would be great to see.
Falcon
Joaquin Torres (Danny Ramirez) is still breaking in his wings after Captain America: Brave New World, with a much bigger threat in front of him.
M'Baku
Winston Duke's M'Baku already commands every scene he's in without any multiversal assistance. The Wakandan King has built his reputation the old-fashioned way, through sheer force of personality, and is set to remain in the MCU through 2028.
Red Guardian
Alexei Shostakov (David Harbour) was conceived from day one as the Soviet Union's answer to Captain America. In a sense, Red Guardian has technically been cosplaying as somebody else's Variant since... now sporting a "cool" new suit.
Sentry
Lewis Pullman returns as the fractured Bob Reynolds, and the moment he fully becomes Sentry, arguably the single most powerful being walking around the MCU, could end up being the biggest swing factor in whether the Avengers stand a chance against Doctor Doom.
Beast
A quick cameo in The Marvels post-credits scene marked Kelsey Grammer's live-action MCU debut as Beast. He's been conspicuously absent from every trailer and teaser released for Doomsday so far, but it is confirmed that he'll have a new look.
Nightcrawler
Alan Cumming teleporting back into the role more than two decades after X2 is the kind of returning legacy casting that is here for nostalgia and fun, but not much more.
Cassie Lang
Don't expect a starring turn from Cassie Lang (Kathryn Newton) this time around, as she was the last cast member given a chair, and she also might be more of a mark for Doom, like most of the other heroes' children are being targeted.
BONUS: Loki
Few characters have logged more multiversal mileage than Loki. Fittingly, the newest trailer places Tom Hiddleston's trickster back in his TVA agent uniform, seemingly pulled from sometime before the Loki season 2 finale.
What To Expect From Hayley Atwell's Peggy Carter In Avengers: Doomsday
It's important to note that the 15-year MCU veteran may not just be returning as the Peggy audiences said goodbye to in Endgame.
Since that film, she's played a full-fledged superhero twice, voicing the super-soldier Captain Carter in the animated series What If...?, then bringing a live-action version of the character to the big screen as a member of the Illuminati in Doctor Strange in the Multiverse of Madness, where that particular Earth-838 Variant met a brutal end with Wanda Maximoff (Elizabeth Olsen) slicing her in two with her own shield.
Which raises real possibilities: whether it's a new multiversal Variant or Peggy simply picking up the shield herself, there's a good chance Atwell steps into Doomsday as a full-blown hero again, not just the wife of Steve and the mother of their child.
No matter how Atwell returns, this will be her 11th MCU project (movies and TV), a ridiculous number. Atwell made her MCU debut in Captain America: The First Avenger, a character she went on to headline in the Agent Carter Marvel One-Shot, two seasons of her standalone ABC series Agent Carter, and flashback appearances in Agents of S.H.I.E.L.D.
Within the mainline MCU theatrical timeline, she played an elderly Peggy visited by Steve in Captain America: The Winter Soldier, appeared in Steve's induced dream vision in Avengers: Age of Ultron, and portrayed a 1989-era S.H.I.E.L.D. Director Peggy in the opening of Ant-Man, before returning for the 1970 Camp Lehigh time heist (and the final dance) with Steve in Endgame.
Just like how the Russo Brothers have said that Steve's return is for good reasons, hopefully that's the case for Peggy, too. In live action, many fans would love to see her actually fight alongside Steve, something that's never really been seen.
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