When the first Iron Man came out in 2008, it would have solely been produced by Marvel. Most thought that the studio was scraping the bottom of the barrel when it came to characters to bring the big screen, but no one could have foreseen the sheer amount of success the movie would garner. Nor would they have guessed about the shared universe of movies and characters that would stem from it. But before the Marvel's massive, billion-dollar success, it was a much tougher time for Marvel, which had to sell the movie rights to some of its biggest characters in the hopes of avoiding bankruptcy.

RELATED: 15 God-Like Marvel Cosmic Beings The MCU Ruined

But now, 10 years later, the Marvel Cinematic Universe is an unprecedented series of movies that has brought to life dozens of Marvel superheroes, from Captain America to Doctor Strange, from the Guardians of the Galaxy to the friendly neighborhood Spider-Man -- and Captain Marvel will soon make her long-awaited debut on top of all that. Although, as massive as this universe currently is, there are still many characters, some very popular, others less, that Marvel still does not have the movie rights to. Today, CBR flips through the Marvel encyclopedia to list 15 characters that still can't appear in the MCU.

15 THE FANTASTIC FOUR

Marvel Comics' Fantastic Four by Jack Kirby

The Fantastic Four is Marvel's first family of superheroes, not to mention one of its most endearing and popular super-teams. Only, their stock has fallen in the comic book world of late, as the team's comic series has been missing from Marvel's titles due to a very complicated situation of movie rights issues. As a matter of fact, those movie rights belong to rival studio Fox, and they don't plan on giving them up any time soon.

This means that Marvel Studios can't bring Mr. Fantastic, The Thing, the Invisible Woman and the Human Torch into its cinematic universe. And since that is the case, Marvel has followed suit by downplaying the importance of the Fantastic Four in the comics, in a bid to achieve corporate synergy. This is all unfortunate, as the team would fit in very nicely with the rest of the cinematic Avengers.

14 VENOM

Venom-Space-Knight

This is where the confusion might start. Before, the rights to the Spider-Man franchise, his supporting cast and his villains belonged to Sony. But, after a string of disappointing movies starring the wall-crawler, Sony and Marvel Studios struck a now famous deal that would allow Spider-Man to appear in the MCU, starting with Captain America: Civil War and going into his own solo franchise.

Meanwhile, Sony is currently in the midst of developing a Venom movie starring Tom Hardy. However, this deal with Sony only involved Spider-Man's appearances in the MCU -- which means that, being solely a Sony production, the Venom movie will not be a part of the MCU, and it will not feature an appearance by Tom Holland. It's actually been stated that this movie will not take place in the Marvel Cinematic Universe, but the Marvel comic book universe -- whatever that means.

13 DR. DOOM

Dr. Doom crossing his arms

Dr. Doom is not only the Fantastic Four's main villain, he is also one of the biggest and most dangerous villains in the Marvel comics universe. He has a long history and rivalry with Reed Richards and Tony Stark, and he has fought the Avengers on many occasions, on a cosmic and temporal scale. But there is still no chance to have Dr. Doom appear in the MCU, with the character's rights still belonging to Fox.

Although Doom's most recent big screen appearance was a disappointment, both financially and critically, the studio still has plans to keep making movies involving the character, with a rumored Dr. Doom solo film teased at Comic-Con in 2017. Sadly, this means that the good Doctor will be in his own universe, and he won't get to interact with the rest of the Avengers, or become the Infamous Iron Man.

12 GALACTUS

The famous planet-eating giant is known for his insatiable hunger and his massive, moon-sized stature. Galactus is a villain, sure, but he is more like a force of the universe, a threat to all worlds, one that would make for a very big and dangerous addition to the MCU. Besides, very recently, in the comics, the character took a heroic turn to become a member of Carol Danvers' Ultimates crew, which means that there would be a lot of potential for his cinematic future.

However, the character is tied to the rights of the Fantastic Four. Translation: he belongs to Fox, which means that Marvel Studios can't use Galactus in its movies. We have no idea if Fox even has plans for the character, but as long as they hold onto the rights, we'll never get to see the likes of the Guardians of the Galaxy go up against this iconic cosmic entity.

11 WOLVERINE

Never X Old Man Logan

Hugh Jackman's take on Wolverine proved to be one of the most popular and successful superhero castings. The actor portrayed the character in a long string of movies, culminating in his lauded, heartbreaking swan song of a movie, Logan. While the actor did go on record to say he would consider returning to the razor-sharp claws, it would only be on the condition that he would get to interact with the Avengers.

However, this remains in the realm of the currently impossible, as long as the character's rights belong to Fox. The studio probably isn't too keen on letting one of its most popular characters go back home, which likely means that, sooner rather than later, we will see a new actor take on the role of the Ol' Canucklehead. Whether that will be in a new X-Men movie, the just-announced X-Force production, or his own movie, remains to be seen.

10 SILVER SURFER

silver surfer

The Silver Surfer is one the foremost cosmic characters in the Marvel comic books. He roams the spaceways on his surf board, teaming up with various members of the Guardians of the Galaxy whenever the threat is too great. He is a popular hero that would prove to be a fascinating addition to the cosmic side of the MCU.

But, just like his master Galactus, for whom he is often a reluctant herald, the Silver Surfer's rights belong to Fox. As he is attached to the Fantastic Four franchise, the character won't be going away from the studio anytime soon. One can only imagine what Guardians of the Galaxy director James Gunn could do with such a surreal and philosophical character, but sadly that is something we may never get to see.

9 DEADPOOL

Deadpool Movie Poster

Deadpool came out of the floodgates kicking and foul-mouthing, taking the world of cinema by storm to become a household name. With this newfound popularity, it seems like the studio who owns the character, Fox, is only just starting a new phase of its universe, with Deadpool at its center: Deadpool 2 is currently in the works and he is also set to co-lead the recently announced X-Force movie.

The character simply isn't part of the MCU, no matter how much the Deadpool movie was trying to tell you otherwise, from nods to Hydra ("Is that you, Bob?") to the inclusion of what looks very much like a decommissioned S.H.I.E.L.D. hellicarrier as the location of the explosive final battle. One can only hope that the powers that be agree to share the character. If anyone could be in two separate universes, it's Deadpool. He'd tell us so.

8 NORMAN OSBORN

Norman Osborn is undoubtedly one of the biggest foes in Spider-Man's life, as well as one of the most important characters in his universe, one he has a long history with. With a sequel to Spider-Man: Homecoming already set to happen, you would be forgiven for hoping for Norman, a character who also has a lot of history in the larger Marvel Universe, to finally make his grand entrance in the MCU.

Unfortunately, as a character from the extended cast of the Spider-Man franchise, Osborn's movie rights still belong to Sony. While the character could hypothetically appear in a Sony movie like Venom or Silver and Black, we may never get to see the villain start up H.A.M.M.E.R. to usher in a "Dark Reign" over the Marvel Cinematic Universe, or see him suit up as the Green Goblin to battle Tom Holland's Spider-Man over the rooftops of New York City.

7 ANNIHILUS

Annihilus-Marvel

Annihilus is an alien creature from another dimension, the Negative Zone, and he has been one of the biggest threats to the cosmic heroes of the Marvel Universe. With his Annihilation Wave, Annihilus was able to launch a full scale invasion of the universe that almost led to the destruction of everything and everyone. But a few heroes, like Drax and Nova, were able to stop him.

While an important staple of the cosmic side of the Marvel Universe, Annihilus was first introduced as a villain to the Fantastic Four – which means that the character, like Galactus and the Silver Surfer, also belongs to Fox. The green alien would be a well-received addition to the MCU, one that could prove to be the main threat in a string of movies in a fashion similar to Thanos. But at Fox, the character may remain woefully unused.

6 THE SHI'AR IMPERIAL GUARD

Avengers Shiar Smasher Gladiator

The Shi'ar Empire is a vast alien race that occupies a very large place in the cosmic side of the Marvel universe. They can just as easily be allies as enemies, and they are very powerful. And nowhere is this more true than when it comes to the Shi'ar Imperial Guard, the elite force of their Empire, a force which counts, in its ranks, popular characters like Gladiator and Smasher.

Smasher was an Avenger for a time, and both she and Gladiator were instrumental in fighting alongside Captain America and his Avengers against the overwhelming force of the Builders in the Infinity event. But the Shi'ar's movie rights are tied to the X-Men franchise, which means that they too belong to Fox. It's likely that the alien race will have a role to play in X-Men: Dark Phoenix, but it's doubtful that Gladiator and Smasher will appear.

5 ROM THE SPACEKNIGHT

Marvel's Rom the Space Knight fighting creatures in space.

ROM The Spaceknight is a beloved character whose situation is quite tricky. While he debuted as an unpopular toy in 1979, the character found new life and popularity with his very own Marvel comic series. In this comic, ROM was introduced as an alien from the planet Galador, a world under threat from the evil Dire Wraiths, and he sacrificed his own life and humanity so he could become a robotic Spaceknight -- a warrior to defend his people.

But as an original toy from Hasbro, the character is owned by Paramount, who eventually plans to use the character in its very own shared universe of movies. The story itself, however, belongs to Marvel. So basically, neither company can use what the other owns, as far as movies go. Guardians of the Galaxy director James Gunn mentioned that he would love to use the Spaceknights further down the line, but unfortunately ROM would not be among them.

4 KANG THE CONQUERER

Hailing from the far-flung future of an alternate reality, Kang The Conqueror originally appeared in the Fantastic Four comic books before becoming one of the bigger villains of the Avengers. A powerful and dangerous time-traveler, Kang's wish is to rule the world in his own image. His character and powers are closely tied with both Reed Richards and Doctor Doom, which makes him another character owned by 20th Century Fox.

Armed with advanced weaponry from the future, the would-be tyrant Kang has fought everyone from the X-Men to Giant Man and the Vision. However, we will never get to see the character become the important Avengers villain he is supposed to be – not in the MCU. And that is too bad, considering that time travel would have been a nice path to explore in Marvel's still mysterious phase four of movies.

3  ABIGAIL BRAND AND S.W.O.R.D.

In the closing moments of the ABC series Agents of S.H.I.E.L.D.'s fourth season, Phil Coulson woke up in a space station, something that had everyone awaiting the full introduction of S.W.O.R.D., S.H.I.E.L.D.'s sister organization protecting the Earth from all manner of space threats. We were also left expecting its director, Abigail Brand, a beloved character to comic fans.

Standing for Sentient World Observation and Response Department, the organization was first introduced in the Marvel comics in Joss Whedon's Astonishing X-Men, just like Abigail Brand, who was revealed to be a mutant. Therefore, the character, as well as S.W.O.R.D., is a part of the X-Men comic books, which means that they are owned by Fox. Alas, this means that wherever Coulson is, it isn't S.W.O.R.D., and he will not get to trade wits with the green-haired agent.

2 NAMOR

Never X Namor

Namor the Sub-Mariner is the King of Atlantis, a half-human, half-Atlantean hybrid with mutant powers. He is often touted as the oldest mutant in Marvel's history of publishing, the first ever to appear in the comics. He is a popular character that has been a part of major events for decades and he has been affiliated with everyone from the Fantastic Four to the Avengers and the Illuminati.

But the character's movie rights are a bit more complicated. For a very long time, the character belonged to Universal, which made it all the more impossible to have the character appear in the MCU. However, there have been more recent reports that say the character could come back to Marvel, but that there are still many legal issues to deal with between Marvel and Universal. And with the time these legal things take, this could go on for a long time still.

1 THE HULK

Wait, what? We know what you're going to say: "That's impossible, because we've seen the Hulk in the MCU, right? He was in his own movie, and then he appeared in the Avengers movies, and he's about to get into a smackdown with Thor in a gladiatorial match for the ages in Thor: Ragnarok. Right?" Yes, that is all true.

But the reality of the situation is that The Incredible Hulk movie was released by Universal, and the studio still owns the distribution rights to a solo Hulk movie – which is why the Hulk now only appears in team-up movies, and not a sequel to his own film. This means that the full movie rights to the Hulk are quite complicated, and we would need lawyers as powerful as the Jade Giant himself to untangle this legal web. Until then, we will be more than content to watch Hulk smash Thor to pieces!

Which character would you most like to see come to the MCU? Let us know in the comments!