When Marvel Comics decided to get into the business of creating films based on its own characters, it entered the world of filmmaking, a wondrous and magical place filled with possibilities, celebrities and of course, unending compromise. You're dealing with so many working parts that plans for "Film A" can change dramatically because of what happened on "Film B" or because "Actor C" has a problem with "Actor D" from a bad relationship 20 years ago. It can be a mess. Even as Marvel Studios was purchased (along with Marvel) by Disney Studios, the same basic idea applies and in fact, because of its high profile, things got even worse.

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Of course, studio involvement and actor management are not the only things that you have to worry about when producing a film. There are lots of strange things that go on behind the scenes in Hollywood -- that's just the business! With all of that in mind, here are 15 strange behind-the-scenes stories about making the films that comprise the Marvel Cinematic Universe. From struggles over scripts, to struggles over what a toy train can do, to one of the strangest Easter Eggs in comics, this list has you covered!

15 MARVEL'S EMPIRE STRIKES BACK EASTER EGG

As you may or may not know, Marvel has split its movie releases into three phases (so far). The first phase was all of the introductory movies and then ended with The Avengers. The second phase ended with Ant-Man and the MCU continuity in the middle of the third phase at the time of this list's writing. The second phase, then, would be the Marvel equivalent of the second Star Wars movie, The Empire Strikes Back. In honor of that film, then, each of Marvel's Phase 2 films include someone losing an arm or a hand.

It started as just a coincidence, with the first couple of films just happening to have people lose their arms. Once they were aware of it, they made a point to keep on doing it in all Phase 2 films, like Klaw losing his arm to Ultron and Yellowjacket's arm becoming decorporealized first in Ant-Man.

14 IRON MAN BEGAN FILMING WITHOUT A FINISHED SCRIPT

The first Marvel Studios film was 2008's Iron Man, which had a lot riding on it. That's why it is so amazing that the film actually started shooting without a finished script! Don't get us wrong, the producers a rough outline of everything that they wanted to have happen in the film, but they figured that shooting without a script would allow them to improvise a lot and give a more authentic performance.

Robert Downey Jr. loved the ability to improvise, but other actors weren't quite as used to this type of filming. For instance, Jeff Bridges, who played Obadiah Stane, was not at all used to this type of filmmaking, but noted that he actually got a kick out of it when it started, later noting that it was like making a "$200 million student film."

13 WHY CAPTAIN AMERICA DIDN'T EAT ANY SHAWARMA

mcu cast eating shawarma in the avengers

The post-credits sequence in The Avengers is a hilarious bit where the Avengers all get together after successfully defending New York City from an alien invasion by getting some shawarma. However, the scene was not actually filmed until after the movie had already had its global premiere! You see, in an earlier scene, Joss Whedon had Robert Downey Jr. improvise a few lines of dialogue. One of them involved shawarma. Whedon didn't use it at first, but then changed his mind and decided to use it.

So the cast got together after the global premiere and filmed the scene. The problem was that Chris Evans had grown a beard for another role and could not shave it off! So they outfitted him with a special prosthetic that made it look like his actual jaw and he just didn't eat any food.

12 WHO IS THOR KISSING?

At the end of Thor: The Dark World, Thor had to return to Asgard to let his father, Odin, know that Thor was not interested in taking over as king from his father. Of course, what Thor did not realize is that when he was talking to "Odin," he was actually talking to Loki in disguise, who had taken the place of Odin (possibly even killing their father in the process).

In any event, Thor then returned to Earth where he had a heartfelt reunion with his beloved Jane Foster, played by Natalie Portman. The two shared a deep kiss.... or did they? You see, due to different filming schedules, Portman was not available to film the sequence with Chris Hemsworth (Thor), so instead they filmed Portman in her apartment seeing Thor but the embrace was actually with Hemsworth's wife, actress Elsa Pataky, wearing a wig and Portman's clothes!

11 JOSS WHEDON FOUGHT TO KILL QUICKSILVER

One of the odder disputes that Marvel had with rival film studio, Fox, was over the rights to the character Quicksilver. Quicksilver debuted in an issue of X-Men, so Fox felt confident that he was included with their general license of all X-Men characters. However, Marvel contested that since he served most of his time in comics as a member of the Avengers, so he would count within the Avengers rights. Eventually, a deal was struck where both studios could do their own Quicksilvers.

Thus, when Joss Whedon wanted to kill him off in Avengers: Age of Ultron, Marvel balked. They had just gone through so much trouble to get him, they didn't want to give him up right away. They made Whedon film a sequence where Quicksilver survives his seemingly fatal wounds. In the end, though, they let Whedon do the film that he wanted and Quicksilver remained dead.

10 SPIDER-MAN LED TO BLACK PANTHER'S ROLE IN CIVIL WAR

Similar to how they negotiated the right to use Quicksilver in Avengers: Age of Ultron, Marvel was also negotiating with Sony over the use of Spider-Man in Captain America: Civil War, which would set up Spider-Man to become part of the Marvel Cinematic Universe in a bold deal between Disney and Sony where Marvel Studios would make the creative decisions on Spider-Man's films going forward while Sony would make all of the money on said films.

In any event, the negotiations weren't going great at one point, so Marvel decided to beef up Black Panther's role in the film (which was originally going to be more like a cameo) to make up for what they were afraid was going to be a lack of Spider-Man in the film. When the deal got done and Spider-Man was allowed to be used, Panther had already locked in a bigger role.

9 THOMAS THE TANK ENGINE DOES NOT KILL

One of the funniest bits in Ant-Man was when the titular hero was facing off against Yellowjacket in the bedroom of Ant-Man's young daughter. They shrunk down and suddenly Cassie's Thomas the Tank Engine train tracks were an imposing danger for the two men while they were fighting. Seeing the (contextually) giant Thomas the Tank Engine barreling down on them was a hoot.

However, amusingly enough, there were some strict conditions Marvel had to agree to to use Thomas. He had to not be portrayed as evil, he could not be used to kill anyone and, very specifically, no one could be tied up on train tracks ahead of him (like old school film villains would do in the pre-talkies era). Marvel agreed and Thomas remained a neutral figure in the story.

8 WHO THE HECK IS "EDWARD HARRISON"?

Edward Norton as The Hulk

On some of the early promotional posters for Marvel's The Incredible Hulk, screenwriter Zak Penn is not the only person credited for the film's story. Some of them list a man named "Edward Harrison." Ultimately, though, when the film officially came out, Penn was the only listed screenwriter. So, who is Edward Harrison?

Harrison was a pen name for the star of the film, Ed Norton, who routinely re-wrote the script to the film throughout his time filming the movie (co-star Tim Roth would recall that Norton would literally re-write the script at least once a day). Norton wanted to be credited for his work, but in the end, the Writers Guild decided that only original screenwriter, Zak Penn, would be credited. That might have played a role in Norton not returning to the role in The Avengers.

7 THE EVER-CHANGING CATCH-UP LIST

One of the big things that Joss Whedon wanted to accomplish in The Avengers was to capture just how disconcerting it was for Steve Rogers to now be living in his future (following Steve being discovered in Captain America: The First Avenger, which led into The Avengers). Whedon filmed a bunch of scenes delving into Steve and his feelings, but ultimately a lot of them were cut for time.

Some of them popped up in Captain America: The Winter Soldier, including a notable scene where we see that Steve has kept a list of things he has to catch up on during his time away. Amusingly enough, in different parts of the world, different lists were used. We're spotlighting the Australia/New Zealand one as well as the Latin American one.

6 HULK'S FAILED SUICIDE ATTEMPT

In the Incredible Hulk comic book, after the death of Bruce Banner's wife, Betty Banner, due to what appeared to be radiation poisoning from being around Bruce too much (it later turned out to be intentional poisoning by one of Hulk's enemies -- but this is comics, so don't worry, Betty came back to life). That shook him greatly and he spent a lot of time just trying to kill himself.

Whatever he tried, though, the Hulk would keep him from dying. When he tried to shoot himself, he would transform before the bullet could pierce his skull. Originally, the film Incredible Hulk had a similar scene. It ended up getting cut from the movie, though, as it was probably a bit too intense for the intended general audience.

5 IRON MAN 3 ADDED A CHARACTER JUST FOR CHINA

In Iron Man 3, there is a minor character named Dr. Wu, played by legendary Chinese film star, Wang Xueqi. Wu is the man who ultimately performs the surgery that removes the arc reactor from Tony Stark's chest so that he doesn't have to rely on it to keep himself alive anymore.

Amusingly enough, there was a different version of Iron Man 3 made just for China, where Wu's role is beefed up and even gained an assistant, played by famous Chinese film star Fan Bingbing, who talked to Wu about how nervous she was over the surgery. He assured her that they were going to save the day. There was also a shot of Iron Man noting that he needed China to save him and he visits a group of Chinese schoolchildren.

4 HOW THE AVENGERS CHANGED THOR: THE DARK WORLD

Loki sitting down in Asgard.

Originally, Thor: The Dark World would have focused solely on Thor and was not going to have Loki in it at all. After Loki was such a smash success as the main villain in The Avengers, however, the Thor: The Dark World script was altered to give a role to Loki. Amusingly, once he was in there, they just wanted to give him even more screen time!

The director of the film, Alan Taylor, referenced how they re-shot the film to add more Loki to it, "We're doing full scenes, scenes that were not in the movie before. We're adding scenes, creating scenes, writing scenes for the first time. We realized how well Loki was working in the movie, and we wanted to do more with him."

3 WHAT TATTOO COULD VANKO NOT HAVE?

Hilariously enough, while Thor: The Dark World was busy adding Loki to the film, Iron Man 2 was busy taking Loki out of the film! The main villain in Iron Man 2 was Ivan Vanko, a mixture of a couple different Iron Man villains, namely the Crimson Dynamo (the Vanko part and the whole "brilliant scientist" part of the character) and Whiplash (the whole whips part of his character).

Vanko was played by Mickey Rourke, who came up with a lot of the ideas for his character by himself, like his gold teeth (which Rourke paid for out of his own money) and being covered in tattoos. Amusingly, he originally had a prominent Loki tattoo that they then decided to use digital effects to erase, as they felt it would make it seem like he had a direct connection to the other villain.

2 A HULK FIRST FOR MARK RUFFALLO

In The Avengers, Mark Ruffalo became the fourth actor to play Bruce Banner in a live action project, following Bill Bixby (from the Incredible Hulk TV series and TV films), Eric Bana (2003's Hulk) and Edward Norton (2008's Incredible Hulk). However, unlike those other actors, Ruffalo has a unique first... he's the first actor to actually play Bruce Banner and the Hulk!

In the TV series, obviously Lou Ferrigno portrayed the Hulk. In the first two Hulk films, the Hulk was created through digital effects and was added to scenes later on, without involvement from Bana and Norton (other people did the motion capture effects). Ruffalo, though, wanted to be in each Hulk scene, so he wore a motion capture outfit during every scene with the Hulk and they used that to mold the Hulk into a digital being.

1 THE MANDARIN LIVES!

When he got down to making Iron Man, while planning the film as a trilogy, Jon Favreau had a big problem with the Mandarin. Favreau wanted the villain, who is the closest thing Iron Man has to an arch-enemy, to be the villain of the first film. The problem that Favreau had was that he felt that the Mandarin was too fantastical of a villain for the first movie, as he wanted to ease into the more outrageous type of villains, as the series went along.

However, originally, the Mandarin was to be the villain of the first movie, with Obadiah Stane being Tony's friend in the first movie before being revealed to be evil and then become the villain of the second movie. Also, of course, in Favreau's original view, the Mandarin was very much a real character, with the terrorist group Ten Rings being his organization.

Can you think of a good Marvel Cinematic Universe secret that we didn't mention? Let us know in the comments section!