The MCU is likely to be remembered as one of the defining cultural milestones of the 21st century. Fully realizing the dream of a successfully interlocking, cross-media shared universe franchise, it has become the cinematic standard for action films through brilliant character work, genuine effort, and stellar writing. One of the main boons the franchise boasts is a consistently amazing cast that revels in bringing comic-accurate versions of beloved Marvel heroes and villains to the silver screen. Chris Evans showed how straight-laced and serious he could be while looking as ridiculous as possible, Scarlett Johansson gave a masterclass in how to be sardonic but likable, and Robert Downey Jr., well…Robert Downey Jr. unveiled himself as the coolest dude ever to cool.

While it’s virtually a given at this point that Marvel will make the best casting call, fans on the internet seem to love speculating and fantasy casting their own favorite actors and actresses as various heroes. While this isn’t necessarily a new phenomenon, the MCU and its cultural presence has shifted this activity from a fun project to an out and out hobby, to the point that entire online articles are written about it. Funny how that happens, huh?

15 EMILY BLUNT AS CAPTAIN MARVEL

As one of the last major Marvel IPs to not get an MCU debut yet, the internet offered up dozens of potential ideas as to who could play Captain Marvel. Among the more interesting notions was Emily Blunt, an actress known for giving fierce, intense performances. Her ability to emote is accentuated by her naturally expressive eyes and her classical training has definitely given her the range necessary to play the strong-willed Carol Danvers.

She probably would have had to dye her hair so she could appease the vocal fans who would insist on having a blonde Captain Marvel, but actors have made greater sacrifices for roles. The biggest obstacle to her playing the role? Apparently not only did Blunt not know she was in consideration for it, but she’d never even heard of the character before.

14 TRIPLE H AS THOR

Years before it revealed wrestler Dave Bautista as a gifted comic actor, a continent of WWE fans believed that Marvel was planning to make sports entertainment superstar Paul Levesque, aka Triple H, into their god of thunder, Thor. Though the rumors were never substantiated, it’s obvious that they were based on Triple H’s in-ring themes of Germanic and Viking mythology.

The fact that most knew him as a long-haired blonde with bulging muscles who actively beat people up for fun and profit probably didn’t hurt. While Chris Hemsworth is quantifiably the better actor of the two, all of Triple H’s previous cinematic ventures having been unsuccessful at best, the sheer surrealness of seeing the man they call the Game swinging a hammer in full metal armor while trying to convincingly come across as regal would have been worth any price of admission.

13 JIM CARREY AS LOKI

Nobody, not even Tom Hiddleston, could have predicted how Loki would explode in popularity following his turn as the main villain in the first Avengers movie. A part of his appeal was the energized mystique around the character. In various scenes, Hiddleston got to show off his range between intense, emotional screaming and cold, subtle scheming, letting audiences know how physical an actor he could be while constantly hinting that he was intentionally holding back his true potential.

Had Jim Carrey been cast in the role, as many fans and some Marvel producers wanted, he likely would have forgone subtlety and gone straight, out-and-out insane. Which, for Carrey, would have basically meant playing it true to life. His physical energy and screen presence are legendary and there’s no way his usually over-zealous performances would have been outrageous scene stealers as, fittingly, the god of tricks and thieves.

12 DONALD GLOVER AS SPIDER-MAN

Donald Glover’s small but significant role in Spider-Man: Homecoming not only put Childish Gambino in the MCU, but hinted that Miles Morales might be right around the corner. However, this cameo was likely brought about by an internet army who believed that the Community star should have played the Ultimate wall-crawler as far back as the ill-fated Amazing Spider-Man movies.

The fan casting was born from Glover’s quick wit, sincere acting style, and him being a self-admitted comic nerd. Glover even brought up the movement in his stand-up special, where he admitted he was intrigued by the idea. When Disney reached an agreement with Sony over the rights to Spider-Man, the same community rose up to reignite support for Glover, but Tom Holland was cast before it could build up enough momentum.

11 SIMON PEGG AS ANT-MAN

One of the biggest disappointments to MCU fans was the split between the Marvel creative team and director Edgar Wright. The British auteur best known for the famous Cornetto Trilogy, three comedy films he did with fellow Brits Simon Pegg and Nick Frost, enthusiastically joined Marvel to direct Ant-Man but ended up leaving before the film was completed due to creative differences. Early in the film’s development, fans started swirling around rumors that Wright was bringing his pal Pegg on board to play the titular role.

Though most were more than satisfied with the performance Paul Rudd delivered as Scott Lang seeking an outlet for personal redemption, it would have been fascinating to see the approach that Pegg, used to playing outsized personalities and caricatures, would have taken in his stead.

10 OSCAR ISAAC AS DOCTOR STRANGE

Doctor Strange was always going to be one of the hardest characters for Marvel to adopt for screen, mostly because the introduction of magic was guaranteed to rewrite the rules and stakes for the entire MCU experiment. To navigate such fragile territory would take an actor with range, craft, and complete control over his screen presence. While nobody could argue that Benedict Cumberbatch did a bad job in the role, the internet had previously suggested a completely different face, that of rising star Oscar Isaac.

Having starred in such flicks as Inside Llewyn Davis, Ex Machina, and Star Wars: The Force Awakens, Isaac has proven himself more than capable of handling potentially controversial roles. His proven acting chops could have taken the performance Cumberbatch gave and elevated it to an even more artistic level.

9 VIN DIESEL AS BLACK BOLT

Believe it or not, there was a period early in the MCU’s planning where Inhumans played a major role. Originally slated as a movie in Phase 3, it was quietly dropped into a television show when it became clear that there was little fan support behind the franchise. Despite that, there was one interesting bit of fan dream casting which circulated around the internet around when Inhumans was first announced. Namely the idea that character actor Vin Diesel could viably play the silent Inhuman king Black Bolt.

The monarch’s powers force him to communicate solely through facial expressions, something Diesel is actually quite gifted at. And since he didn’t have to talk in the role, he could pull double duty and still voice everyone’s favorite Groot! But when the project was downgraded into a television show, Diesel stopped being a viable option and Anson Mount was cast instead.

8 JOSEPH GORDON-LEVITT AS ANT-MAN

The biggest element of appeal for the Ant-Man movie was its heavy emphasis on comedy, something that was suspected as soon as it was announced that Edgar Wright would be directing the film. Within hours, fans were wondering which talented comic actor would be taking the title role. Among the names mentioned was Joseph Gordon-Levitt, who had proven himself to be worthy of comic book movies by approaching his role in The Dark Knight Rises with the exact right level of seriousness.

His noted comic timing could have maintained the humorous edge the movie had, but his range as a dramatic actor would have played up the more tragic elements of the story. There’s no knocking Paul Rudd’s performance, the man is rightfully known as a national treasure, but Gordon Levitt is just capable of a broader variety of acting styles.

7 GWENDOLINE CHRISTIE AS VALKYRIE

In Thor: Ragnarok, Tessa Thompson blew audiences away with her portrayal of Valkyrie as a jaded, sardonic bounty hunter. However, when it was first announced that Valkyrie would be appearing in Ragnarok, fans believed the character would be similar to the divine figure in the comics. And for many fans, there was only one actress qualified to play such a strong, unwavering role: Gwendoline Christie.

Having proven herself a talented and versatile performer in other works, Christie was known to most as the morally righteous Brienne of Tarth, one of the soul voices of outright compassion on HBO’s notoriously dark Game of Thrones. The similarities between the two characters, as well as Christie’s strikingly Nordic appearance, caused many to imagine her in the role. Thompson’s performance was laudable, but it may have deprived viewers of a more traditional Valkyrie.

6 DAN STEVENS AS IRON FIST

As of this writing, Iron Fist and The Defenders are the only two Marvel projects that could be classified as outright failures, and one of the main albatrosses to Defenders is that it had to feature Iron Fist. A major reason for this is the unfortunate casting of Finn Jones as the eponymous hero. In truth, Iron Fist was always going to be a complicated character to bring to the modern, more socially conscious era, but Jones was just unable to convey the innate tragedy of a character trapped between two worlds, neither of which would fully accept him for his ties with the other.

Long before Jones was even a possibility, however, fans speculated that if the Defenders were ever integrated into the MCU, Dan Stevens of Downton Abbey fame could feasibly bring the right tone to the story. Frankly, anyone could have been better than Jones.

5 NIKOLAJ COSTER-WALDAU AS CROSSBONES

Even after the character has been cast, debuted, gone through a logical and satisfying story arc, been apparently killed off, and be rumored to be returning, admit it; deep down you want Marvel to retroactively recast Crossbones so you can somehow see Jaime freaking Lannister try to kill Captain America. A rumor started sometime early in the production of Captain America: Winter Soldier, fans wanted to witness the classically trained Danish actor of screen and stage bring his unique level of realism to the secondary villain.

While Frank Grillo certainly played Crossbones to the best of his ability, even emphasizing the humor of his tragic predicament in Civil War, we are left wondering what an intense, naturalistic performance Coster-Waldau could have churned out between seasons of Game Of Thrones.

4 BILLY ZANE AS THE VULTURE

There’s no arguing that Michael Keaton’s return to comic book films was a welcome turn for the actor who brought a reinvented version of the classic Spider-Man villain the Vulture to life. But when the antagonist of Spider-Man: Homecoming was still speculation, fans published entire lists online of potential villains and actors to play them. One of the more prominent suggestions was Titanic actor Billy Zane as Vulture.

Not only does Zane pull off Vulture’s classic bald look, but his in-your-face acting style would be just the right amount of intensity to play the version Marvel presented to audiences, that of a desperate man trying to keep his family financially stable by any means necessary. While it was awesome to see Keaton back at what made him famous to begin with, Zane has is own history with comic book movies and he deserves a chance at redemption.

3 TOBEY MAGUIRE AS SPIDER-MAN

The Sam Raimi Spider-Man trilogy from the early '00s arguably lay the groundwork for what would become the MCU. In the same era where all superhero movies were sporting leather dusters and gritty realism, Rami reminded viewers that superheroes could be colorful and playful without sacrificing quality or maturity. The fourth instalment in the franchise was never made and Marvel moved on to the fledgling MCU not long after.

When it was announced that Captain America: Civil War would feature the MCU debut of Spider-Man, a small but vocal faction of fans believed that reinstating Tobey Maguire as the web-slinger would be the right move. Not only would it be a return of a familiar actor to a familiar, almost groundbreaking role, but it would retcon the origins of the MCU, starting it as far back as 2002.

2 H. JON BENJAMIN AS ROCKET RACCOON

On the surface, hiring Bradley Cooper to voice a character that was essentially Bradley Cooper but as a robotic raccoon sounds like a good idea, if a little insane out of context. But just before the casting was announced, the internet proposed an alternative: famed voice over artist and actor H. Jon Benjamin, whose distinctive deep and gravelly voice was responsible for bringing to life the likes of Sterling Archer, Bob Belcher, and Carl the Convenience Store Clerk.

As a professional in the world of voice acting, Benjamin would have come with preemptive knowledge of how to handle a character from behind a microphone and he would be the perfect voice of the anti-social, temperamental rodent cyborg. There’s no debating that Cooper did a good job, but just imagine the performance that could have come from a seasoned pro.

1 RONDA ROUSEY AS CAPTAIN MARVEL

When it was announced that a Captain Marvel movie was slated somewhere in Phase 3 of the MCU, one of the first popular fantasy castings was that of former UFC women’s bantamweight champion ‘Rowdy’ Ronda Rousey. The celebrated MMA fighter and Olympian had already had minor roles in Furious 7, Entourage, and The Expendables 3, but her acting chops had never been really put to the test.

That being said, she certainly looks the part, with a face used to conveying intensity and a level of fitness that would lend itself to superheroic stunts. Many fans were inspired to create photoshopped posters of her in the character’s iconic uniform. Rousey herself seemed to be completely behind the fan casting and even reached out to Marvel execs hoping to open negotiations. While Kevin Feige himself seemed to be in her camp, the company eventually decided to go with Brie Larson.