What If...?'s first episode asks the question, "What If...Peggy Carter was the First Avenger?"
That's followed by a retelling of Captain America: The First Avenger as Steve Rogers' one-time love interest is given the opportunity to take the Super Soldier Serum and head into action in his place. That's not the only big change to this timeline, though, as a butterfly effect follows that creates a world unlike anything we ever saw in the MCU.
All of that is going to have consequences for this reality, and perhaps even the one we've become so familiar with since 2008's Iron Man was released.
Captain Carter's introduction looks set to be a bigger deal than you think, and this premiere expertly sets the stage for a series that's going to drive home just how important the Multiverse is moving forward...
6. Peggy Carter's Fateful Decision
The first episode of What If...? drives home the point that even the smallest decision can change everything, and that's emphasised when Peggy decides to keep a closer eye on Steve's transformation.
As a result, the bomb was that little bit closer, and both Steve and Colonel Phillips were gunned down before the former could be transformed into Captain America. Luckily, Steve survived, but it was Peggy who took the Super Soldier Serum in his place and then became the hero known as Captain Carter.
From here, it's clear that What If...? will reveal what happens when even a minor change to history is made. However, we can't help but wonder what happens when it's something a lot more major!
5. Bucky Barnes Doesn't Become The Winter Soldier
With the Tesseract falling into Allied hands that little bit sooner, the train Captain Carter leads the attack on has a different purpose: it's a moving bomb meant to kill her and Steve Rogers.
However, because the HYDRA Stomper takes the brunt of that blast, Peggy and the rest of the Howling Commandos survive. That includes Bucky, who never falls to his apparent death, and certainly doesn't wind up in HYDRA's hands to be brainwashed and turned into their Winter Soldier.
We don't know if Arnim Zola still performed some of those early experiments on Bucky, but it seems this is a world that will never have a Winter Soldier. That could majorly weaken HYDRA's infiltration of S.H.I.E.L.D. and the U.S. Government and might mean Bucky simply got to live a normal life.
4. The Original Iron Man
With the Tesseract in his possession, Howard Stark dreams up a way to give Steve the opportunity to still be a hero. Building a suit of armor that's powered by the Infinity Stone, Tony Stark's father creates "Iron Man" decades before his son is even born.
We're assuming Steve continued heading into action as the near-indestructible HYDRA Stomper in the years that followed Peggy's apparent demise, but what sort of impact would this have had on Tony? Perhaps he was never kidnapped by the Ten Rings in this timeline, and we're willing to bet there were enough ripple effects from Howard's creation to ensure Iron Man never existed.
Given how crucial he was in the present day, it feels a lot like Captain Carter's world could suffer the consequences of the HYDRA Stomper's existence - perhaps that explains why we've seen her protecting a desolate New York City alongside an unfamiliar group of Avengers in the trailers?
3. Red Skull's Demise
With a very different plan to his MCU counterpart, this Red Skull instead chooses to use the Tesseract to bring a mysterious creature to Earth as HYDRA's "champion" (we'll get to that).
Unfortunately for the villain, his plan backfires and he's promptly killed. There's no coming back from that, and this Red Skull was clearly never sent to Vormir to become the unwilling guardian of the Soul Stone. Marvel Studios has never explained the circumstances behind that or if someone served in that role before Red Skull, but this could prove to be significant for this world.
The Infinity Stone may now be unprotected, and with no one there to enforce that whole "soul for a soul" rule...well, we're not sure what exactly that means. Whatever the case may be, this Red Skull doesn't leave much of a lasting impact, but the creature he summons quite possibly will.
2. Shuma Gorath?
Shuma Gorath is a demonic creature believed to be the main antagonist in Doctor Strange in the Multiverse of Madness. Apparently, Gorath sets his sights on Xochitl Gomez's America Chavez because he wants to use her powers to have complete control over the MCU's Multiverse.
Chavez has the power to jump freely between realities, and for an all-powerful creature such as this, being able to make reality itself bend to his will by travelling from world to world would obviously make him an unstoppable force not even the Sorcerer Supreme and Scarlet Witch can stop. What we're wondering, though, is whether the Red Skull's "champion "is also Shuma Gorath!
The similarities are impossible to ignore, and the HYDRA leader may have unwittingly brought the monster to his Earth now that the walls between dimensions have been weakened by the Multiverse's rebirth. This could even be what altered the demon to the existence of other worlds!
1. A New First Avenger
Decades later, Nick Fury and Hawkeye use the Tesseract not to bring Loki to Earth, but to retrieve Captain Carter from wherever she's been all this time. She hasn't aged a day and seems unaware that decades have passed, but it's possible her fight with that monster continued for at least a few moments before she was "put on ice."
What could she have seen during that time? Well, we wouldn't be surprised if Carter had time to cross paths with Doctor Strange and the Scarlet Witch, thereby explaining the rumors she will make a live-action cameo in the upcoming sequel.
As this MCU's new First Avenger, we clearly haven't seen the last of Captain Carter. In trailers for What If...?, she's been shown interacting with other heroes, so this soldier's fight isn't over yet. Beyond that, however, we fully expect to see more of her (especially as it's been confirmed she'll be part of season two as an unexpected ally to The Watcher).