13 MCU Theories That Were Too Good to Be True

A cameo from Tom Cruise as Iron Man? A Mysterio-disguised Loki? Mephisto in ...everything?? We take a look back at the MCU theories that seem laughable now.

Avengers: Endgame
Photo: Marvel Studios

This article contains MCU spoilers

As a comic book fan, you go into superhero movies with some expectations. When Nick Fury shows up to talk to Tony Stark about the Avengers Initiative, you know to be excited. When Volstagg refers to the Tesseract as an “Infinity Stone,” you know that things are about to get real. When Doctor Strange meets a man named Mordo, you know that this relationship isn’t going to work out. And when Captain America is menaced by a longhaired assassin with a metal arm, you know what face lies beneath the mask.

That’s not to say that you know everything that’s going to happen! None of the movies or shows in the Marvel Cinematic Universe are entirely faithful to the source material. Probably the closest would be Captain America: Civil War, and that one is still way off from the comic.

Between the knowledge that comes from the comic book page to the serialized nature of the MCU to the limited scope we’re given in the trailers (which sometimes go out of their way to fool us), how can you not theorize on what’s next? Sometimes this pays off. The moment Steve Rogers nudged Mjolnir in Avengers: Age of Ultron, many knew that he was going to one day slam that thing upside Thanos’ head. Even theories that sounded weird like Stan Lee being a Watcher and Peter Parker being the kid in the Iron Man mask from Iron Man 2 were turned official down the line.

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That’s not what we’re here for today. Today, we’re going to look at the fan theories that just did not pan out. Ones that seem silly now but were borderline believable back in the day.

Phil Coulson Will Become the Vision

Vision’s origin is a mouthful no matter what continuity you go with. Avengers: Age of Ultron was able to make it work, but they had to jump through a lot of hoops in a movie that was already busy enough. One of the biggest changes from the comic was taking out the part where Vision’s personality was copied from the “brain patterns” of Simon Williams, a character who has still yet to appear in the MCU outside of being an Easter egg in a deleted scene from Guardians of the Galaxy Vol. 2. Instead of going that cloned mind route, they repurposed JARVIS and plugged him into the red synthezoid body.

But one popular theory after the first Avengers movie was that Agent Phil Coulson was going to be resurrected as Vision at some point. He had the same calm demeanor, and he was just too likable a character to just get rid of. Shove his mind into an advanced robot body and you have a classic Avenger reimagined.

That’s not what happened, but it still is not too far from Coulson’s actual fate. His mysterious return was the selling point of Agents of SHIELD, and while the initial rumor that he was brought back as a Life Model Decoy was a red herring, he was eventually resurrected as an LMD late in the series. Close enough!

Loki Will Be Thanos’ Advisor

In the comics, Thanos snapping out half of life in the universe was only the beginning and not a climactic Empire Strikes Back ending moment. Not only that, but using the Infinity Gauntlet had no physical drawbacks and anyone could use the six stones repeatedly without worrying about being fried from cosmic energy. That meant that wielding the Infinity Gauntlet made you omnipotent and a true force to be reckoned with.

Thanos was so much of a threat that Mephisto, Marvel’s “Satan, but not really, but really” was relegated to following Thanos around in an advisory role. He was obviously plotting to stab him in the back the first opening he got, but he was also scared shitless of what Thanos could do to him and spent much of the story biding his time.

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Loki had already been Thanos’ underling in the MCU. The limited amount of footage in the Avengers: Infinity War trailer showed him being subservient to the Mad Titan, offering the Tesseract. Even before the trailer hit, the popular theory was that Loki would fulfill the Mephisto role. He would spend much of Avengers: Infinity War at Thanos’ side, both kissing up to him and offering advice. All the while, he would be waiting to strike in hope of taking the Infinity Gauntlet for himself.

Instead, Loki lasted only a few minutes before getting his neck crushed. I suppose he did fulfill the theorized role, just as a speed run.

Thanos Loves Hela

It wasn’t until Avengers: Infinity War came out that we knew why Thanos wanted the Infinity Stones. Only then did we realize that he was being written as an insane Jor-El with an axe to grind when it came to overpopulation. Up until then, it seemed like he was obsessed with Death like in the comics. Hell, his intro scene in Avengers played with the idea by having him smile at the idea of “courting Death.”

With Thor: Ragnarok coming out months before Avengers: Infinity War, that opened up the possibility that Hela the Asgardian Goddess of Death was going to be a stand-in for the feminine Grim Reaper from the comics. Thanos’ reign of terror would be a way to honor and win the love of Hela, who could have been brought back after the destruction of Asgard.

While this did not come to pass, Thanos and Hela did briefly become an item in the comics around this time.

Karen Will Become Venom

Like Vision, Venom is a complicated character to introduce…unless you’re having the symbiote literally fall out of the sky out of nowhere and handwaving it like in Spider-Man 3. The possibility of Venom in the MCU had an extra wrinkle because Sony was doing a Venom solo movie that sidestepped Spider-Man’s involvement. How do you introduce the symbiote without making it TOO similar to the prominent box office star? There is always the Ultimate Spider-Man way where it was a manmade biological experiment gone wrong!

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Spider-Man: Homecoming inspired a theory that the MCU Venom would not be a living creature, but artificial intelligence grown out of control. Spider-Man’s Stark-made suit had the AI called Karen speaking through it. Karen acted as Peter’s JARVIS counterpart throughout the movie and had control over the suit’s various abilities. What if Karen went bad or obsessive? In a time when Tony Stark was experimenting with nanotechnology, what if Spider-Man’s suit gained sentience and became a problem?

Not only would this make a unique cinematic version of Venom, it would also act as a retelling of the Iron Man storyline “The Man in the Iron Man,” where one of Stark’s armors went berserk and tried to kill its creator.

This did not come to be, of course. Instead, they just found a roundabout way of bringing in a sliver of the Venom symbiote from the Tom Hardy incarnation’s universe.

We Have Already Seen the Soul Stone

Going into Avengers: Infinity War, five of the six Infinity Stones were accounted for. The movie used the final stone’s reveal as a major plot point and a vehicle to give us a shocking death scene (plus a shocking death scene in the sequel). It wasn’t apparent that the Soul Stone was being saved for Infinity War, so that had people guessing about how it was going to show up.

One idea was that the Soul Stone was in Wakanda. Perhaps it was part of the vibranium meteor that crashed there so many years ago. It could have even been responsible in some way for the magical herb that gives the Black Panther his power. After all, Black Panther was coming out only two months before Infinity War and the trailer showed that Infinity War’s final battle was going to take place in Wakanda. What better reason for Thanos to invade than to grab a stone that was being protected there?

There was some truth in that idea, but nothing having to do with the Soul Stone.

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Another idea was that Heimdall was somehow linked to the Soul Stone. Maybe he was even powered by it! The Soul Stone being connected to somebody being able to see all life across the universe? I can buy that. More importantly, Idris Elba was reaching the point where he was too big a star to be playing such a relatively minor role, so either they were going to make him way more important or they were going to have to kill him off ASAP.

Kill him off ASAP it is.

Wolverine Fought Thanos

Are the markings on Thanos’ face genetic or are they scars? That’s what people speculated when we got such a good look at him in the Infinity War trailer. One idea that was spreading a bit was that Wolverine tangled with Thanos at some point. That’s why the markings on his face resemble the telltale adamantium claw scratches.

This was before Disney bought out Fox, but considering Spider-Man getting to pop up in Captain America: Civil War, it wasn’t impossible for Fox to reach a deal for Disney to introduce a new Wolverine into their continuity. Besides, Fox had killed their Logan just a year earlier, so they were not going to be stepping on any toes there.

Bucky Barnes Will Also Be Captain America

During the first several years of the MCU’s existence, Bucky Barnes was Captain America in the comics, wearing a glossy outfit and carrying a gun. Steve Rogers died in the aftermath of the Civil War event and Bucky took up the mantle. While he had gone back to being the Winter Soldier by the time Captain America: The Winter Soldier hit theaters, the expectations were there.

The seeds were also planted. In all three Captain America movies, there is always a moment where Bucky is shown wielding the vibranium shield. The whole thing feels like blatant foreshadowing for a passing of the torch we’re destined to see down the line.

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Months after the release of Captain America: The Winter Soldier, the mantle changed yet again in the comics. Sam Wilson took over as Captain America. That complicated the MCU’s path a bit and made it a coin toss over who was going to take over once Chris Evans was done. Bucky still has a future in the MCU, but not wearing the red, white, and blue.

Captain Marvel is a Skrull

Before we knew the full story of Carol Danvers’ backstory of being kidnapped and gaslighted by the Kree, we had her initial movie trailer. One of the important things to take out of it was her determined attitude in embracing who she really is. This happened to be for a movie where she’s fighting aliens known for shapeshifting and stealing people’s identities.

Several years before the movie’s production, Marvel did the big Skrull-based comic event Secret Invasion. One of the highlights was the company’s original Captain Marvel (Mar-Vell) returning from the dead, only to be revealed as a Skrull sleeper agent given the powers and memories of Mar-Vell to help fulfill the mission. The truth tore the Skrull apart with confusion as he did not know whether to fight the Skrull Empire or do their bidding. Eventually, he decided to die opposing them.

Putting it all together, it looked like the big, obvious twist in Captain Marvel was that Carol Danvers was going to be a Skrull sleeper agent all along. There were indeed some twists in there relating to Skrulls and Carol’s identity, but she’s proved she isn’t one of them by…shooting a jukebox with her laser hands.

Yeah, Fury was right to question that as proof.

Mysterio is Loki from Avengers: Endgame

This is a theory I personally insisted on back in the day, but looking online, I’m far from the only person to come to this conclusion. Mysterio showed up in the trailers for Spider-Man: Far From Home. He insisted on being a superhero from elsewhere in the multiverse and emphasis was put on him being like a cross between Thor and Doctor Strange.

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Anyone who knows anything about Mysterio knows that he’s not on the level. His whole deal is that he’s a villain who uses trickery to mess with Spider-Man’s perception of reality. Of course he wasn’t really a superhero. That said, was there more to him? This was after Marvel revealed that the Mandarin was a dopey actor and the Skrulls were sympathetic refugees. There had to be a twist for people who knew what to expect with Mysterio. Was he really just going to be the guy we know from the comics?

Before the Loki show was announced, Loki’s Avengers: Endgame cameo seemed too important to just be a throwaway moment. He escaped with the Tesseract and was a gigantic loose thread. Something was going to happen with him. Also, as explained in Thor: Ragnarok, Loki knows that his reputation on Earth is forever ruined. Therefore, what if Mysterio was really that Loki all along? It would add to Mysterio’s claims that he was from another Earth, as it would technically be true. What Loki wanted out of it was up in the air, but the setup was there.

Welp. Turned out Mysterio was just going to be the guy we know from the comics.

WandaVision Will Lead to the Mutant Age

Disney had bought Fox, and suddenly X-Men and Fantastic Four were on the table to use in the MCU. That’s easy enough for Fantastic Four, but not so much for X-Men and mutantkind in general. After over a decade of worldbuilding, how can you simply state that mutants have been around all along? There needed to be a plot-driven catalyst for it. Considering the comics mostly wiped out the mutant race via House of M, a story where Wanda Maximoff went insane and created a new reality with her powers, perhaps they could do the opposite with the MCU?

WandaVision was a show where Wanda was using her powers to create a new reality. It was a show that made vague allusions to House of M and made a very blatant meta reference to the Fox X-Men Cinematic Universe with the recast Pietro Maximoff. Wanda even created her own children who had powers and a sense of self. If there was ever an excuse to go big and introduce mutants to the MCU, this was the time.

The Engineer is Somebody Major

I could make most of this list just WandaVision theories, like what people thought was going on with the mysterious beekeeper and the reaction to Paul Bettany’s joke about acting with someone he’s always wanted to do a scene with (being himself in the Vision vs. Vision battle). People did go a bit overboard with the guessing games, but sometimes the setup feels so blatant that it’s hard to blame viewers for thinking something is up.

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Like that time Monica Rambeau talked up how she had somebody in mind who could make a very special, top-of-the-line rover that could break through Wanda’s forcefield. It felt so much like they were setting up some kind of reveal, like Reed Richards, Adam Brashear, or Hank McCoy. There was no special payoff to that plotline and the vehicle didn’t even solve the problem.

I suppose that the whole situation could have been related to Monica being aware of loyal Skrulls working within SWORD – something revealed in the finale’s mid-credits scene – but the whole thing felt like a letdown.

It Was Mephisto All Along

Ah, the big one. Early on in WandaVision, it was established that this was definitely Wanda’s doing. Then they kept building and building anyway so we had to imagine there was more to it. Agnes turned out to be Agatha Harkness, who was treated as a mastermind, but in actuality, she was just guiding Wanda’s madness.

In the comics, when Wanda had to come to terms with her children being magical constructs, the big villain turned out to be Mephisto. With some Devil references and imagery here and there throughout the show, people were prepared for Mephisto to be set up as the next big villain in a post-Thanos world.

That did not turn out to be the case, but he remained on everyone’s tongue. The first episode of Loki directly compared Sylvie to the biblical Devil. Spider-Man: No Way Home was partially based on a comic storyline where Peter Parker sold his marriage to Mephisto so that people would forget his secret identity. Plus there was another Doctor Strange movie on its way and Mephisto could have easily meshed with that.

Who knows if we’ll ever get Mephisto in the MCU. It will be a Boy Who Cried Wolf situation for sure.

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Tom Cruise is Illuminati Iron Man

A lot was going on in the first trailer for Doctor Strange in the Multiverse of Madness, but not enough for us to have any idea what was going on. The big talking point was the introduction of the Illuminati and its shocking inclusion of Patrick Stewart as Charles Xavier. There were plenty of rumors of who would make up this Illuminati and debate of whether they existed in one world or were banded together from across the multiverse.

The shot of Ultron drones in the trailer pointed in the direction of a corrupt Tony Stark being in charge of things. We’ve seen different variations of evil Iron Man in the comics over the years, from the Dr. Doom variation in Exiles to the Iron Maniac in Marvel Team-Up, but the most memorable take was the greedy and amoral Superior Iron Man.

If we were going to see this Stark variant pop up, he couldn’t be played by Robert Downey Jr. No, that guy is absolutely done with the role. Being a multiverse story, they could throw practically anyone in there without having to worry about long-lasting canonical consequences or multi-picture contracts. That had people bent on the idea that Tom Cruise – once up for the role of Tony Stark so many years ago – would be playing the Superior Iron Man.

Even when the leaks came out of the actual line-up, fans refused to give up. Maybe there would be a post-credits reveal or something. Nope. Instead, we got a post-credits scene of Bruce Campbell doing slapstick, which is by definition superior to anything Tom Cruise does.