While the trailers for Spider-Man: Far From Home haven't revealed much, they've introduced a Mysterio who seems out of place compared to most other incarnations of the character.
Instead of being an outright villain who uses special effects to create illusions to attack his enemies, he's apparently a magical hero from an alternate reality who has come to the Marvel Cinematic Universe for help. At least, that's what he claims to be. He could still easily turn out to be the ultimate villain of the film, with the apparent monsters attacking Europe being some form of illusion of his own making.
However, a new fan theory suggests he could actually be a different Marvel villain in disguise. If accurate, this could go a long way to explaining his apparent abilities. Although it's very unlikely due to various real-world factors, the fan theory that Jake Gylennhaal is actually secretly playing Doctor Doom is still a fun idea to consider.
As posted to Reddit by user Wildmasny, the theory centers on some specific qualities about how Mysterio introduces himself. Nick Fury introduces him as Quentin Beck, who has arrived on this world through a tear in reality caused by the use of the Infinity Gauntlet in Avengers: Endgame. Instead, the fan theory suggests this is an assumed name taken on by the villain. The theory argues that the character is actually Victor Von Doom from another timeline.
The theory points out that Doctor Doom's mastery of both technology and magic would provide a good explanation for his apparent powers. Throughout the trailer, Mysterio is also seen apparently utilizing the same kind magical maneuvers that Doctor Strange and other sorcerers have used elsewhere in the universe. This could all be an illusion, but these "illusions" seem to be doing some serious damage to the cities they're attacking. Those are some radically powerful illusions. If these powers are real then Mysterio is a particularly powerful character, and all of that power could easily point to Myterio's identity as Doctor Doom.
Finally, the Reddit user brings up how the Elemental villains in the trailer have a passing resemblance to Doom's greatest adversaries, the Fantastic Four: The creature that appears to be Sandman could be a stand-in for the Thing, while Molten Man could easily be a substitute for Human Torch. Hydro-Man represents Mister Fantastic in this comparison. While that doesn't answer where the Invisible Woman analog is, it is a fun parallel to draw attention to.
Mystic Master And Genius Inventor
First introduced in Fantastic Four #4 by Stan Lee and Jack Kirby, Doctor Doom has gone on to become one of the most definitive villains at Marvel. A scientific genius and a gifted sorcerer, Doctor Doom has made for a formidable villain for almost every hero in the universe at some point or another. He's easily one of the most dangerous men in any reality he calls home.
In the trailer for Spider-Man: Far From Home, Mysterio is shown creating massive magical blasts while zipping around in an empowered suit. He looks like a cross of Doctor Strange and Iron Man, two of the biggest heroes in the MCU. If it's real, all that power would only make sense coming from someone like Doom.
Marvel did also just procure the rights to Doctor Doom, along with the rest of the Fantastic Four and X-Men. The acquisition of Fox by Disney means the producers behind the MCU now have access to most of the superhero universe for their upcoming films. While Spider-Man: Far From Home has been billed as an epilogue to the world-shaking events of Avengers: Endgame, it could be a stealth introduction to the future biggest bad in the MCU. There's no way Doctor Doom won't be appearing in the MCU at some point.
Why It Won't Happen
There are a couple of realistic reasons why Mysterio is almost certainly not Doom. Spider-Man: Far From Home has been in development for far longer than it took for the Disney/Fox merger to fully come into effect. It's unlikely that Marvel would have risked derailing the film with a detail like that in case the deal didn't go through. Due to the nature of the negotiations between Disney and Fox, Marvel might not have had the legal right to include Doom.
Spider-Man: Far From Home is also a co-production with Sony, who still technically own the cinematic rights to Spider-Man and his universe. There's no reason for Sony to want to use the film to promote a non-established character that it doesn't have a stake in. Frankly, a Sony-owned character like Venom would have a much better chance of making it into the film instead of Doctor Doom.
There's also no reason to believe that Marvel would try to sneak Doctor Doom on audiences like this. He's one of the publisher's biggest bad guys and is one of the few who's anywhere near the same caliber as Thanos. Introducing him as a last-minute plot twist in a relatively low-stakes Spider-Man film would be one of the strangest decisions in the entire history of the MCU.
Furthermore, Feige has hinted that the Fantastic Four and X-Men won't appear in the MCU until Phase 5. While that all-but-disproves the theory, the idea of Mysterio secretly being Doctor Doom in this film is still fun to think about.
Opening July 2, director Jon Watts’ Spider-Man: Far From Home stars Tom Holland, Samuel L. Jackson, Zendaya, Cobie Smulders, Jon Favreau, JB Smoove, Jacob Batalon and Martin Starr, with Marisa Tomei and Jake Gyllenhaal.