When they first arrived into Hollywood in 2008 with Iron Man on their backs, Marvel Studios was a much smaller movie studio than it is now. Heck, Marvel, in general, was a smaller... everything back in the day. The superhero genre itself was not nearly as popular as it is now, but today, the Marvel Cinematic Universe has helped Marvel becoming a superpower in itself in Hollywood as many of its films rank among the highest-grossing ever.
Much of that is due thanks in large part to the financial backing from Disney, who bought Marvel in 2009. Of course, while they allow Marvel creative range to do most of what they want, Disney still has the final say in who Marvel decides to bring on to their projects. Yes, even if they were in the MCU before, Disney has to give the final O-K before that actor or actress makes it to the set. There are some actors who Disney will never give that O-K to.
20 Edward Norton - Hard to work with in last Hulk movie
The Incredible Hulk was Marvel's second-ever movie in the MCU, but its story has been largely ignored since Edward Norton never reprised his role as Bruce Banner. It has been well documented that Marvel opted to not bring him back because of creative differences.
In a statement released in 2010, Marvel basically said Norton wasn't a team player and was hard to work with, so that nixes any idea of him returning even in a separate role.
19 Wesley Snipes - Difficult to work with
Marvel has just cast Mahershala Ali to play Blade for the Marvel Cinematic Universe. Obviously, the previous actor who played him - Wesley Snipes - is too old to play him, but don't expect a cameo or supporting role from him either.
There's a reason why Snipes isn't in big Hollywood movies anymore. On the set of Blade: Trinity especially (Patton Oswalt said he often went "crazy" onset), Snipes built a rep as someone hard to work with.
18 Terrence Howard - Domestic abuse case & dispute from Iron Man
Nevermind the fact that Marvel doesn't want to deal with Terrence Howard anymore after he was fired from playing Rhodey in Iron Man 2 due to a salary conflict. In the years since reports have surfaced of Howard being an alleged domestic abuser.
Given Disney's squeaky clean image, they won't risk it on an actor who didn't even work out well last time.
17 Shia LaBeouf - Off The Rails
Shia LaBeouf was a beloved Disney child star in the early 2000s starring in Even Stevens, but in his more adult years, the man has been a handful in the public eye.
He's been at the center of strange performance art displays, public drunken disputes, multiple arrests and has been meme'd to death. Don't expect Disney to take a chance in bringing back their golden child when he's become such a crazy man.
16 Halle Berry - Ruined Catwoman
Before the superhero genre was as beloved as it is today, it was something of a joke in the public eye. Most of which is because of movies like Catwoman stinkin' up the joint.
To this day, that film remains one of the worst in the genre and earned Halle Berry a Razzie for Worst Actress. Given how badly her last superhero movie turned out, Marvel probably won't hire her for one of theirs.
15 Tobey Maguire - Bad Spidey history
With the MCU/Sony deal falling apart, the role of Spidey is open now, but don't expect a throwback actor to fill it. While Tobey Maguire many fans' favorite onscreen Spider-Man (if only for nostalgia), he wasn't the easiest Spidey that Hollywood had to work with. People forget that he actually got fired from the role in 2003 after failing to negotiate a more lucrative contract.
Sony even went as far as to have meetings with Jake Gyllenhaal about playing Peter Parker in Spider-Man 2 before Tobey basically begged for his job back.
14 Shailene Woodley - They dropped her as MJ
A little known fact is that The Amazing Spider-Man 2 actually featured Shailene Woodley as Mary Jane Watson, but all of her scenes were deleted from the final cut. She thought she would get a larger role for the third Spidey film, but Sony canceled that.
Instead of offering her a part in the MCU, they went and hired Zendaya as MJ instead. Marvel must not want anything to do with Woodley.
13 Andrew Garfield - flopped as Spiderman
Andrew Garfield is often viewed by fans as the worst actor to play Spider-Man. Even those who carry a soft spot admit his films were the worst in the history of the character, garnering both critical and financial plummets.
Rather than take another crack at him for their MCU, Disney and Sony wanted an entirely new Spidey and recast him with Tom Holland.
12 Robert Pattinson - Playing Batman
Robert Pattinson has done a fine job at navigating through Hollywood in his post-Twilight career. He went from being an annoying teen actor everyone hated (or they hated Edward, at least) to a critically acclaimed award-winning actor thanks to roles in films like Good Time.
He could make a fun addition to the MCU, but sadly, Marvel doesn't want him since he'll now be playing the biggest superhero property from their competition, Batman.
11 Ronda Rousey - Turned her down as Captain Marvel
Ronda Rousey is one of the few athletes to make a huge impact both as a legitimate MMA fighter and a professional wrestler. To her disappointment, she'll probably never make an impact as an actor among the MCU. She actually campaigned to play Captain Marvel to the point she started training for it when Marvel was looking for an actress.
Kevin Feige said he liked the idea of her playing the character, but since he hired Brie Larson as the character, he must not want Ronda in the MCU.
10 Charlie Sheen - Way too controversial
Oy vey. Where do we even begin with Charlie Sheen? Well, we'll never forget that he was kicked off of Two and a Half Men after a crazy run-in squabble with a prostitute at a hotel.
Then, we learned that he knowingly had unprotected sex with HIV without telling his partners, which his exes have since sued him over. That barely tips the iceberg, but it's enough that Disney has no intentions on hiring him.
9 Bella Thorne - Says she hated growing up on Disney
Bella Thorne got her big break in the acting industry by starring in a Disney Channel show called Shake It Up. Years later, well into adulthood, she went on The Jenny McCarthy Show to say that not only did she hate working for Disney, but she also hates having to live up to that "perfect" image that comes with being a Disney child star.
Obviously, you don't badmouth The Mouse, so Disney won't be trying to hire her for anything any time soon, let alone the MCU.
8 Hugh Jackman - Too recognizable as Wolverine
Hugh Jackman is probably the one name on this list that Disney wouldn't mind hiring, but there's one problem that conflicts with Marvel's plans: he's too recognizable as Wolverine.
Obviously, he won't reprise the role any time soon as he exited it following Logan, but with the MCU gaining the rights of X-Men, they'll be looking to cast a new, younger Wolverine. Having a former Wolverine in the MCU is just too distracting.
7 Jennifer Garner - Flopped in past Marvel movies
Jennifer Garner played Elektra in both Ben Affleck's Daredevil and a spin-off film of the same name. However, Garner has admitted that she only returned to the role out of contractual obligations, not for any passion or interest in the character or material.
Even worse, both films Elektra did so poorly at the box office that it soured Hollywood on making anymore female superhero movies for over a decade. Marvel might think she's bad luck.
6 Katherine Heigl - Bad mouths cast/crew
Katherine Heigl is only just rejoining the mainstream entertainment industry after joining the TV world for Suits, but don't expect her to rejoin Hollywood anytime soon. She has been notorious for openly badmouthing the people she worked with. When Knocked Up came out, she accused it of being a sexist movie despite starring in it.
Then, she opted out of the Emmy race during Grey's Anatomy's fifth season because she thought the material she was given was weak. A blabbermouth is a problem Disney don't want to deal with.
5 Joaquin Phoenix - Turned down Dr. Strange
Marvel already came knocking on Joaquin Phoenix's door to join their Cinematic Universe as Doctor Strange, and he turned them down. Not only that, but he went on join enemy lines of DC by playing The Joker for an upcoming self-titled origin story.
Both Marvel and Disney might take it personally and won't be handing Phoenix any offers again.
4 Jennifer Lawrence - was hard to work with as Mystique
During the latest franchise of X-Men movies, Jennifer Lawrence played Mystique, but we hardly saw her in the blue makeup and body paint. Lawrence has gone on record in saying that she hated sitting in the makeup chair for 7 hours during shooting.
It was also rumored that she hated playing the part in general after becoming acclaimed for her serious work. Don't expect Marvel knocking on her door next.
3 Ruby Rose - Batwoman for the competition (DC)
Ever since her star-making turn on Netflix's Orange is the New Black, Ruby Rose has gone from model to breakout actress who everyone wants to work with. She may have even been on Disney's shortlist to be in a Marvel movie once upon a time ago.
However, she is now playing Batwoman for The CW. Since Disney is in the TV business now with Disney+ and since Marvel is in competition with DC, she is basically competing with both Marvel and DC now.
2 Ben Affleck - Flopped as Batman + in/out of rehab
Now that he's out of DC's Batman, Ben Affleck is free to pop up in the Marvel Cinematic Universe, but given how most fans didn't love his performance as the character (and that's being generous), Marvel may be reluctant to give him another crack at anyone's cowl.
Doesn't help that he has also been in and out of rehab these past couple years.
1 Alexandra Daddario - True Detective
As stated earlier in this article, Disney has always had a squeaky clean image and expect the same image out of their actors. While Alexandra Daddario has far from a bad public image, her reputation precedes her as the girl who went topless in True Detective.
You don't usually see actors who bare all (pun intended) wind up in Marvel movies or Disney movies.
Sources: timenownews.com, screencrush.com