Here are some theories on how Captain Marvel will enter Avengers: Endgame. Marvel Studios has finally kicked off the marketing campaign for Avengers 4, but they took a different approach than expected in debuting the first trailer. Despite massive fan excitement, there was no official build up to the release, with Marvel electing to just drop it online early one morning. But that was nothing on what it did and didn't show.

The Avengers: Endgame trailer focused primarily on the original six Avengers, with each of them getting at least a scene or two. After the Decimation that took place in Avengers: Infinity War, the remaining heroes are clearly reeling: Iron Man (Robert Downey Jr.) is on his last breath in space; Captain America (Chris Evans) is shown crying; Thor (Chris Hemsworth) is isolated and defeated; Bruce Banner (Mark Ruffalo) is struggling to account for those they lost; Black Widow (Scarlett Johansson) struggles to put into words what Thanos did; and Hakeye (Jeremy Renner) has ditched his usual bow and arrow for a new sword to become Ronin. As bad as things appear though, the arrival of Ant-Man at the end of the trailer added some levity and even a potential solution to the problem at hand.

Related: Everything The Avengers: Endgame Trailer Didn't Tell You

Ant-Man and Nebula are the only characters who weren't original heroes to get proper screen time in the trailer, meaning there were several notable characters absent from the Avengers 4 trailer. And none was more surprising than the lack of an appearance by Carol Danvers aka Captain Marvel (Brie Larson); she was positioned in Avengers: Infinity War's post-credits scene as the universe's potential savior, but any resolution to Nick Fury's page was held back. Since we know she is a major part of Avengers: Endgame in some form, though, here are a few possible ways Captain Marvel could be introduced in the movie.

Captain Marvel Could Save Tony Stark From Space

Tony Stark touching helmet in ship in Avengers Endgame

One of the most likely ways that Avengers 4 could introduce Captain Marvel is through a scene that takes up the first minute of the teaser. The Endgame trailer starts with Tony Stark stranded in space (presumably with Nebula) aboard the Benatar, the Guardians' ship. Tony is trying to send a message to Pepper Potts telling her that he's out of food and water and will soon be out of oxygen; he has seemingly accepted his ultimate fate will be death, as he says, "Part of the journey is the end." But, as dire as the circumstances appear to be, he'll be surely saved: this scene also looks to be from the opening of the film and it is highly unlikely that Marvel Studios would kill their biggest star so early on and in such a non-heroic way. Tony is in need of saving and could be how Captain Marvel comes into the picture.

Related: Avengers 4 Theory: Captain Marvel Saves Tony Stark In Space

This would hinge on Carol Danvers being in the same part of space as Tony Stark. Without yet seeing Captain Marvel, what she is doing at the time of Thanos' snap remains up in the air. If she's alive and fighting in space, then it's not too difficult to imagine her seeing or sensing the Benatar floating adrift in space and for her to come to the crew's rescue; after Fury's page, she'd likely be heading to Earth, which is where Tony's presumably charted the spaceship to go also.

Although this could make for a rather convenient meeting between the two, it wouldn't be that surprising a narrative turn in the MCU. Avengers: Infinity War had the Guardians intercept the Asgardian distress signal to find Thor, then wind up on Titan at the exact same time as Iron Man, Doctor Strange and Spider-Man. In addition to quickly getting Captain Marvel involved in Avengers: Endgame, it also gives Marvel Studios an early opportunity for Carol Danvers - arguably the future face of the franchise - to meet and save the life of their original poster child in Iron Man.

Page 2 of 2: How The Quantum Realm or Time Travel Could Introduce Captain Marvel

Captain Marvel in the Quantum Realm with Thanos and Ant-Man

Captain Marvel Could Be In The Quantum Realm With Ant-Man

The Iron Man theory relies on Carol Danvers still being active when Avengers: Endgame begins, but what if she isn't actually in this dimension at all? Her whereabouts for the past twenty years is a major question that fans have and is something Marvel will have to address in Avengers 4 - unless they do so at the end of Captain Marvel.

Aside from her not being allied with either the Kree or Skrulls, where the movie will leave Carol is unknown. However, with it already theorized that Captain Marvel's powers will be in some ways tied to the Quantum Realm, there is an alternative to her being in space; she could be trapped in the Quantum Realm, potentially as a result of the final fight. This would make her the second Avengers: Endgame character to spend time dealing with the microverse, as Ant-Man and the Wasp ended with Scott Lang (Paul Rudd) also being trapped in the realm.

Related: Avengers: Endgame Trailer May Debunk Time Jump Theory

Captain Marvel could then be introduced in Avengers 4 as an ally to Ant-Man in the Quantum Realm, with the pair working together to escape. This would be another easy way to get Carol into the story, and would explain why she hasn't aged since the 1990s without resorting to Kree DNA rewriting.

Captain Marvel Could Still Be In The Past

A much simpler - albeit shocking - avenue to explain Captain Marvel's absence from the MCU for two decades, while also introducing her in Avengers: Endgame, could be through the past via time travel. One of the prevailing theories for how the surviving heroes will bring back those who were dusted is by traveling through time (the Avengers 4 trailer even offers a few possible teases to time travel). If the team ends up back in the 1990s, it could be at this point where Carol Danvers joins the plot; they come across an earlier version of Carol and she helps stop Thanos before really knowing of the Mad Titan.

Quite how this would fit with Avengers: Infinity War's post-credits scene is unclear - it could be that Captain Marvel was a victim of the snap and the team goes to get an earlier version of her - but this would certainly be a mind-bending way to bring a new hero in the Avengers fold, one that means Endgame is dealing with the earliest points of the MCU as well as the most recent.

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These are just a few possibilities for how Avengers: Endgame could introduce Carol Danvers. Once Captain Marvel actually comes out, we will all have a much clearer understanding of how the movie does or doesn't set up Brie Larson's next MCU appearance. More information could come before then once the next Captain Marvel trailer and additional information for Avengers: Endgame are released, but until then this will remain a subject ripe for speculation.

MORE: Every Update You Need to Know For Avengers: Endgame

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