Marvel's What If...? TV series is bringing back 25 Marvel Cinematic Universe actors, so that they can tell alternate versions of various events that have happened throughout the MCU's first three phases. Note that, as of right now, Marvel is planning on only providing twists to Infinity Saga movies, not anything that comes in Phase 4.
In 1977, Marvel Comics debuted the What If...? series, and has published 13 volumes overall. Conceptually, What If...? focuses on major franchise events, and theorizes how different character actions would affect the storyline. The comic series uses various narrators, allowing for different perspectives. Given the MCU’s worldwide reach, the upcoming Disney Plus series What If...? will undoubtedly please fans who have long agonized about controversial plot points. Even more, the new What If...? series won’t be restricted to just the MCU, so the featured performers can be purely creative with their commentaries and ideas.
The animated What If...? series will premiere during summer 2021. As with the original comic series, Uatu the Watcher (Jeffrey Wright) will narrate. The first episode will explore what might’ve happened if Peggy Carter became Captain America and if Steve Rogers transformed into Iron Man. Here's a full list of Marvel actors who will participate in the What If...? series.
Michael B. Jordan as N'Jadaka aka Erik "Killmonger" Stevens: Jordan made his MCU debut in the Oscar-winning film Black Panther. Thanks to the character's black ops accomplishments, the Oakland native received his moniker, Killmonger. Killmonger is killed by T’Challa in Black Panther.
Sebastian Stan as Bucky Barnes aka Winter Soldier: Stan made his MCU debut in Captain America: The First Avenger, and has since appeared in Captain America: The Winter Soldier, Captain America: Civil War, Avengers: Infinity War, and Avengers: Endgame. Stan will star in the upcoming Disney Plus series The Falcon and the Winter Soldier. Bucky is a childhood friend and protector of Steve Rogers.
Josh Brolin as Thanos: Brolin first appeared in Guardians of the Galaxy and became the MCU’s Big Bad. Thanos disposed of numerous superheroes in Avengers: Infinity War, thus setting up the conflict for Avengers: Endgame. Thanos was decapitated by Thor, and ultimately defeated - through time travel - by Tony Stark.
Mark Ruffalo as Bruce Banner aka Hulk: Ruffalo debuted in The Avengers, and reprised the role in Iron Man 3's credits scene, Avengers: Age of Ultron, Thor: Ragnarok, Avengers: Infinity War, and Avengers: Endgame. In Ruffalo's most recent appearance as Hulk, the character embraces his public persona as Smart Hulk.
Tom Hiddleston as Loki: In 2011, Hiddleston made his MCU debut as the God of Thunder's adopted brother in Thor. Since then, Hiddleston has appeared in five more installments. Loki is killed by Thanos in Avengers: Infinity War, but later appears in Avengers: Endgame. Hiddleston will reprise the Loki character for a Disney Plus series of the same name, Loki.
Samuel L. Jackson as Nick Fury: Jackson appeared in the first MCU film, Iron Man, and has since reappeared in eight additional installments. In 2019 alone, Nick Fury was part of Captain Marvel, Avengers: Endgame, and Spider-Man: Far From Home (as Talos). After Quentin Beck attempts to ruin Peter Parker’s reputation, Nick Fury decides to get back to work.
Chris Hemsworth as Thor: Hemsworth made his debut as the aforementioned God of Thunder in the 2011 MCU film bearing the character's first name. Most recently, Thor decapitated Thanos in Avengers: Endgame, and then fattened up before rejoining the Avengers. Thor is currently with the Guardians of the Galaxy, this coming after naming Valkyrie as New Asgard’s ruler.
Hayley Atwell as Peggy Carter: Atwell made her MCU debut in Captain America: The First Avenger as a British agent. After appearing in three more franchise films, Atwell returned for Avengers: Endgame. Steve Rogers travels back in time all the way to the 1940s, where he reunites with Peggy. The couple then grows old together. Atwell has portrayed Peggy Carter in the TV series Agents of S.H.I.E.L.D., Agent Carter, and Avengers Assemble.
Chadwick Boseman as T'Challa aka Black Panther: Boseman first appeared as T'Challa in Captain America: Civil War and was the central focus in Black Panther. After becoming a victim of the infamous Thanos snap in Avengers: Infinity War, he’s revived by Bruce Banner in Avengers: Endgame.
Karen Gillan as Nebula: Portraying a space pirate, Gillan first emerged in Guardians of the Galaxy. After two more franchise appearances, Nebula travels back in time and kills her past self, but ultimately survives because of time travel technicalities. She’s currently with the Guardians of the Galaxy.
Jeremy Renner as Clint Barton aka Hawkeye: Renner joined the MCU for Thor and The Avengers. In 2019, Avengers: Endgame marked Renner’s fifth franchise film, with his character going by “Ronin” after losing his family via the Thanos Snap.
Paul Rudd as Scott Lang aka Ant-Man: After three franchise films, Rudd reprises his electronics expert character in Avengers: Endgame. Lang helps defeat Thanos and returns to Hope van Dyne aka Wasp and daughter Cassie.
Michael Douglas as Hank Pym: The veteran film actor debuted in Ant-Man as a founding member of The Avengers. Douglas returned for Ant-Man and the Wasp, and appears as both a 1970 version and present version of himself in Avengers: Endgame.
Neal McDonough as Dum Dum Dugan: After portraying the S.H.I.E.L.D. officer in Captain America: The First Avenger, he hasn’t appeared in a feature film since. However, McDonough did reprise his role in the short film Agent Carter and the ABC series of the same name.
Dominic Cooper as Howard Stark: Portraying the founder of Stark Industries (Tony’s father), Cooper made his MCU debut in Captain America: The First Avenger. Since then, he’s just appeared in the 2013 short film Agent Carter, along with five episodes of the aforementioned ABC series of the same name. In Avengers: Endgame, John Slattery reprises his Iron Man 2 role as Howard Stark.
Sean Gunn as Kraglin (and Other Characters): Gunn portrays Kraglin in Guardians of the Galaxy, and also did motion capture for Rocket. Gunn reprised the Kraglin role in Guardians of the Galaxy Vol. 2, and once again provided motion capture for Rocket in both in Avengers: Infinity War and Avengers: Endgame.
David Dastmalchian as Kurt: In the MCU, Dastmalchian only appeared in Ant-Man and Ant-Man and the Wasp. Soon, Dastmalchian will crossover into the DCEU to portray Polka-Dot Man in The Suicide Squad.
Stanley Tucci as Abraham Erskine: In 2011, Tucci portrayed the German WWII scientist in Captain America: The First Avenger. The character treats Steve Rogers with Super Soldier Serum, only to be killed by Heinz Kruger.
Natalie Portman as Jane Foster: In Thor, Portman first appeared as the astrophysicist and title character's love interest. For the MCU storyline, Jane allegedly dumps Thor after he pursues the Infinity Stones. Portman appears in Avengers: Endgame through archive footage from Thor: The Dark World, and will lead the upcoming Thor: Love and Thunder as a new version of Thor.
Taika Waititi as Korg: Waititi directed Thor: Ragnarok and will soon helm Thor: Love and Thunder. However, as an MCU actor, Waititi has voiced the Kronan character in both Thor: Ragnarok and Avengers: Endgame. He’ll reprise the role for Thor: Love and Thunder. Korg most recently fought Cull Obsidian in the battle against Thanos.
Toby Jones as Arnim Zola: Thus far, Jones only portrayed Captain America’s supervillain nemesis in Captain America: The First Avenger and Captain America: The Winter Soldier, along with one episode of the ABC series Agent Carter.
Djimon Hounsou as Korath: Hounsou portrayed the Starforce member in both Guardians of the Galaxy and Captain Marvel. Korath is presumably killed by Drax the Destroyer, but appears as his younger self while battling against Carol Danvers.
Jeff Goldblum as Grandmaster: As the ruler of Sakaar, Goldblum made his MCU debut in Thor: Ragnarok. Goldblum's Grandmaster is the Collector's brother.
Michael Rooker as Yondu Udanta: Rooker portrayed the Ravager leader Yondu in Guardians of the Galaxy and Guardians of the Galaxy Vol. 2. Yondu sacrifices his life to save Peter Quill.
Chris Sullivan as Taserface: Sullivan's one and only MCU appearance came in Guardians of the Galaxy Vol. 2. As a Ravagers lieutenant, Taserface is known to be quite dumb and is often disrespected became of his contrived bravado. The character dies during a ship explosion.