With ten years of history and nearly two dozen movies, the Marvel Cinematic Universe has held the attention of its fans steadfastly. Few other cinematic series have lasted as long or had as immediate of an impact on culture and filmmaking. Some of today’s most popular characters, like the Guardians of the Galaxy, were B-list characters at best, with little or no major fan following until their movies were released. Watching the massive increase in popularity for these characters was nothing short of amazing. Suddenly, our favorite characters had the spotlight in a way we’d never imagined!

In the age of the internet, such a major cultural milestone as the MCU is bound to stir up conversation of all kinds, including theories as to the direction of the MCU itself. After every new MCU release, it seems there are unanswered questions, new characters, and limitless possibilities for the future. It doesn’t take long to find lists of theories about what might happen in Avengers 4 and beyond, and what’s fascinating is the possibility that any of those theories may be spot on. Seriously, it’s not that far-fetched. Just take a look at some of the things that have happened in the Marvel Cinematic Universe so far. Some of the biggest events started as nothing more than unfounded fan theories. From the roots of some of our favorite heroes to the fates of some of Marvel’s most classic villains, here are just 20 of the fan theories out there that turned out to be exactly right.

20 RED SKULL SURVIVED

Red Skull at his post on Vormir in Infinity War

One of the earliest movies in the MCU, Captain America: The First Avenger introduced his infamous nemesis, the Red Skull, to the MCU. As the leader of Hydra, the Red Skull was said to be even more evil than anything we've seen before, and was planning the complete takeover of the free world and the regime he represented. At the end of the film, he held the Cosmic Cube, and was seemingly destroyed.

However, many fans theorized that the Cosmic Cube was more than meets the eye --  it was the Space Stone. As such, it had likely teleported the Red Skull somewhere else in the universe. Viewers of Avengers: Infinity War would find this theory to become reality when the character returned as an immortal guardian of the Soul Stone.

19 SPIDER-MAN JOINING THE MCU

civil war spider-man

One of the other theories that Captain America: Civil War’s announcement caused was that Spider-Man would also be pulled into the MCU somehow. This seemed incredibly unlikely as Sony owns the rights to Spider-Man, and had recently suffered losses from the massive flop that Amazing Spider-Man 2 ended up being. But still, Spider-Man played a fairly large role in the Civil War comic event, so fans expected to see him show up.

And show up, he did. Marvel and Sony struck a deal to share the character, and allow Marvel some creative input on Spider-Man’s solo movies. In return, Marvel got to use Spider-Man in any Avengers movies they wanted. He made his first MCU appearance in Captain America: Civil War and continued on in Spider-Man: Homecoming, Avengers: Infinity War, and will appear again in Avengers 4 and Spider-Man: Far From Home.

18 STAN LEE IS A WATCHER

Guardians of the Galaxy Stan Lee Watchers

For a while, Stan Lee’s cameos were nothing more than fun little jokes within each of the Marvel movies. He’d pop up in any movie, no matter which studio was making it. He’s the only thing that unites all of the various Marvel franchises over the years. Fans came to theorize that his omnipresence across the different films meant that there may be more to the character than meets the eye -- he could be a Watcher, one of the aliens who is charged with witnessing the important events that occur throughout history.

This theory came true in Guardians of the Galaxy: Vol. 2, where we see Stan Lee filling in the Watchers on several of the events that he’s seen. Whether he’s a Watcher, a friend of the Watchers, or something else entirely is still up for debate, but nonetheless, fans were a lot closer than they might have expected.

17 THE EYE OF AGAMOTTO IS AN INFINITY STONE

Doctor Strange Time Stone Eye of Agamotto

It’s hard to believe that something that is addressed so directly was originally just a fan theory, but by the time Doctor Strange had been announced, fans were searching for Infinity Stones harder than Thanos. Several had already been confirmed -- the Reality Stone in Thor: The Dark World, the Space Stone (or Tesseract) in The Avengers, the Mind Stone in Avengers: Age of Ultron, and the Power Stone in Guardians of the Galaxy.

Fans felt certain another Infinity Stone was coming in the first film featuring the Sorcerer Supreme. With the evidence of a few hints of the time-based powers of the Eye of Aggamotto, fans assumed that the stone would be the Time Stone. They were totally right, as the fact that it was the fabled Time Stone was openly stated in the movie.

16 THOR BECOMES KING

It had been teased since Thor first hit theaters that Thor was destined to become the king of Asgard. Throughout the first movie, he struggled to prove himself worthy, during The Avengers and Thor: The Dark World, he learned that he didn’t really want to be a king. So, when time came for the third movie, fans assumed that somehow Odin would pass away and Thor would be forced to take the throne he never wanted.

The events of Thor: Ragnarok, while being Thor’s most fun movie, were also some of the darkest and most troubling for the God of Thunder. He lost an eye, his hair, his father, and his home. Somehow, he was expected to still go on and lead his people forward. Fans were proven right, and then some.

15 PETER PARKER IN IRON MAN 2

In Iron Man 2, there is a kid in an Iron Man mask who stands up to one of Whiplash’s drones with a toy Iron Man hand blaster and Iron Man lands behind him, blasts the drone and says, “Good job, kid!” Once it was announced that Spider-Man would be joining the MCU, fans liked the idea that this kid was a young Peter Parker.

Tom Holland likes the idea, and Kevin Feige has more of less agreed that it’s a nice notion, so it’s generally accepted that this may as well be the case. It adds a little more history between Peter and Tony -- imagine Peter seeing Tony in his living room as a 16-year old after having been rescued by him years earlier. It makes that moment, and their relationship, a heck of a lot more meaningful.

14 SKYE IS QUAKE

Skye is the main protagonist of Marvel’s Agents of S.H.I.E.L.D. As the audience’s point-of-view character, she learns about the MCU and S.H.I.E.L.D.’s role as we do, and so, as we learned more about her, fans started to piece together just who she might be. Certain character details -- that she was an Agent and that she was an orphan -- alongside certain plot elements, like the introduction of Mr. Hyde and the Inhumans, all pointed to the idea that Skye would ultimately be revealed as Quake, an Inhuman from the comics.

As those who watch the show know, this is exactly how events played out. Though the Inhumans haven’t played a very large role in the greater MCU as a whole, they’ve had their best representation in Agents of S.H.I.E.L.D.

13 VISION'S FATE

Considering Vision had an Infinity Stone implanted in his forehead, this one was kind of a no-brainer. Fans assumed that, for Thanos to succeed in his quest to gain the Infinity Stones and destroy half of all life in the universe, he’d need to take it from Vision, and he’d presumably do so by force.

Yes, fans missed some of the finer plot details, like that the Avengers would try to remove it without destroying Vision, or that Wanda would destroy the Mind Stone and end Vision, only for Thanos to turn back time and get the Mind Stone anyway. But still, at the end of the day, fans were absolutely right, and Thanos decimated Vision to take the Mind Stone, the last of the six he needed.

12 VALKYRIE’S HISTORY

In the comics, Valkyrie is your standard pale, blonde-haired, blue-eyed, Norse woman. When Thor: Ragnarok introduced the MCU’s Valkyrie, she was portrayed by Tessa Thompson, who didn’t match the look at all. Fans theorized that perhaps this wasn’t the Valkyrie from the comics, whose name was Brunhilde, but another Valkyrie entirely. Furthermore, they theorized that the blonde-haired, blue-eyed woman who lays down her life for Tessa Thompson’s Valkyrie may have not only been her lover, but she may have also been Brunhilde.

At least some of this has been confirmed by Tessa Thompson herself, who stated definitively that her character was bisexual. The rest may be coincidental, but it would be a cool homage to the comic version of the character if it were also true.

11 THE QUANTUM REALM

ant-man-quantum-realm

After Scott Lang had his first brush with the Quantum Realm in Ant-Man, fans knew it was only a matter of time before he’d be back in it. Given that the Quantum Realm exists beyond time and space, it only makes sense that you could travel great distances in both in a seemingly short period. Fans theorized that Ant-Man would get Janet out of the Quantum Realm, but that some characters would become stranded, and this would be how they would survive the infamous “snap.”

Ant-Man and the Wasp proved these theories true, with Janet also confirming that time travel was possible in the Quantum Realm. Now fans theorize that the Quantum Realm’s time travel capabilities will be a major factor in the upcoming Avengers 4 movie.

10 GAMORA'S END

In the Infinity Gauntlet, Thanos stops at nothing to get and keep the Infinity Gems, including disposing Gamora, whose soul is absorbed into the Soul Gem by Adam Warlock. Thus, fans figured that Gamora would meet the same fate in Avengers: Infinity War. While they didn’t know the exact details, fans figured that Thanos would somehow end his adopted daughter.

And of course, he did, sacrificing her so he could gain the Soul Stone. However, this was perhaps his only moment where he showed he was capable of some kind of love. Though some fans may have guessed that it was coming, no one wanted to have guessed right. Still, if her soul is trapped in the Soul Stone, it gives us hope for her and our other favorite heroes.

9 RAGNAROK

If you know anything about Norse mythology (or Marvel comics), you know that Ragnarok is the end of Asgard and the ultimate destruction of the realm. So, when Thor: Ragnarok was announced, fans assumed that meant ultimate destruction in many ways. It was fair to assume that Asgard would be destroyed in some way, and fans were excited to see it.

Maybe no one quite expected what we got: an ultimate showdown between Surtur and Hela that could only end in the utter annihilation of the home world of Thor and his people. It was tragic, it was astonishing, and it was an epic way to end a rollercoaster ride of a movie. It truly raised the stakes for Marvel in a way that few movies had before, and that was just a taste before Infinity War.

8 A PLANET HULK MOVIE (SORT OF)

thor ragnarok gladiator hulk

When Hulk decided to fly away at the end of Avengers: Age of Ultron, some fans noted that he seemed to be staring at the sky as he looked out of the Quinjet’s cockpit. Not long after, it was revealed that he was going to head to space. Fans put two and two together and hoped this meant they could expect to see some kind of adaptation of the famous "Planet Hulk" storyline. This was seemingly impossible, though, considering that the movie distribution rights for a Hulk-based movie belong to Universal Studios, not Marvel.

Still, fans were right and parts of "Planet Hulk" served as inspiration for Thor: Ragnarok. The gladiator scenes were pulled almost directly out of the comic, for example, and the elements of overthrowing a dictatorship are present as well. It’s not a perfect adaptation, but it’s the best we’re going to get for now.

7 CIVIL WAR

Captain America Civil War Team

From the get-go, the Avengers were always an uneasy alliance. They argued more than they worked together in the first movie, almost destroying a helicarrier in the act. By the time the second movie came around, the team was already at odds, particularly after they discovered that Tony was the reason their new foe had been created. Fans saw the writing on the wall and figured it was only a matter of time before some kind of superhuman registration act and superhero civil war akin to that of the comics.

When Captain America: Civil War was announced, fans’ assumptions were confirmed. For some fans, this was a dream come true; others felt that the movie version of events didn’t live up to its comic counterpart.

Hulkbuster Armor Avengers Infinity War

Sometimes fan theories come from the strangest of places and in this case, Lego toys spoiled some things. There was a Lego set for Avengers: Infinity Warwhich showed Bruce Banner piloting the Hulkbuster gear, so fans assumed he’d be inside it -- and hoped for a scene in which the Hulk busted out of the Hulkbuster. It made some sense: the Hulkbuster gear was a lot of fun, but it made fans question why Bruce might not be hulking out at the time- would he and the Hulk be separated somehow?

While we did get Bruce inside the Hulkbuster, we didin’t get the Hulk busting out of it -- maybe that will have to wait for Avengers 4. This isn’t the first time that Legos have spoiled Marvel movies, either, as a Lego set showed fans that Ant-Man would turn into Giant-Man in Captain America: Civil War.

5 LOKI TRIES TO TRICK THANOS

Loki is the MCU’s iconic trickster. He’s constantly double-crossing everyone, from his parents to his brother to his allies -- he is on no one’s side but his own. So, when fans saw his eye on the Tesseract in Thor: Ragnarok, they assumed that he’d grab it, and that Thanos would force him to hand it over. Of course, Loki being Loki, fans assumed he’d have a trick or two up his sleeve and try to end Thanos before giving over the Infinity Stone.

The opening scenes of Avengers: Infinity War proved this theory correct rather rapidly. Loki attempted to stab Thanos with a blade he’d had hidden, and his neck was easily broken by the Mad Titan. While we’re supposed to believe this demise is permanent, fans believe that resurrecting Loki will be a part of Avengers 4.

4 KILGRAVE’S “RETURN”

Kilgrave Jessica Jones

Jessica Jones on Netflix was a major hit; here was a superhero with her own solo TV show dealing head on with many mature themes. JJ is a complicated character whose morality and sense of heroism is questionable; she’s doing the right thing, but is she doing it for the right reasons? Part of what made her story work so well was how despicable the villain was.

Kilgrave was a character whose depth was performed perfectly by David Tennant, and so fans were eager to see him make some kind of return, and assumed that he would, since his performance was so well-received. He did return in season two of the show, but not as a living character, just as a flashback in Jessica’s own mind. Still, it’s more of a return than many Marvel villains have gotten.

3 RETURN OF GENERAL ROSS

William Hurt as General Thunderbolt Ross in a dark gray room in Captain America: Civil War.

When Captain America: Civil Warwas announced, all kinds of theories were shared. Some thought the Thunderbolts would be introduced, with General Thunderbolt Ross at the helm and Abomination as the group’s Hulk. Some thought that the Netflix characters would get pulled into the mix. While not all of the theories were true, the idea that Ross would return was a theory that held more weight than the others.

He did, in fact, return, as someone who was pushing for regulating superhumans. He has since reappeared in Avengers: Infinity War, as well. There’s still been no sign of the Thunderbolts, though, or of Ross becoming Red Hulk, as he does in the comics. There’s still plenty of time, though. Who knows what could happen in Phase Four and beyond?

2 DOCTOR STRANGE ARRIVES

This started as a small tease in what could have been a throwaway line in Captain America: The Winter Soldier. In it, it’s offhandedly mentioned that Hydra has been tracking anyone that it deems a threat, including Stephen Strange, Tony Stark, and others. At the time, there had been no previous mention of Stephen Strange, and there would be no talks of a movie for some time, yet, so the idea that he did exist in the universe was new. Fans immediately began talking about an upcoming movie featuring Doctor Strange.

Ultimately, Doctor Strange did get his own movie, and went on to play a small role in Thor: Ragnarok, and a much larger role in Avengers: Infinity War. He should be returning for Avengers 4, and it’s believed that there will be a second Doctor Strange movie, as well.

1 SOMEONE ELSE PICKS UP THOR’S HAMMER

Vision holding Thor's hammer in Avengers: Age of Ultron

Thor’s hammer is one of those artifacts that presents an impossible challenge, which makes it impossible to resist. If you are “worthy” of the power, you can lift the hammer. What exactly qualifies one as “worthy” in the hammer’s judgment is anyone’s guess, but up to a certain point, only Thor had proven himself worthy, and so only Thor could lift the hammer. Fans figured it was only a matter of time before someone else would pick it up. Theories abounded as to who, as many characters have lifted the hammer before in the comics. Captain America seemed the most likely candidate.

However, in Avengers: Age of Ultron, Cap could only wiggle the hammer. It ended up being the Vision who, unaware of the stipulation, lifted the hammer to hand it to Thor. So, fans had the wrong character, but they were right about someone lifting it.