The Marvel Cinematic Universe defined the last decade. They were able to bring to life some of the most popular comic book heroes ever created. Another reason why these movies were such a hit was that Marvel Studios could sow little easter eggs and hidden references into the film that keep fans coming back for more.
Whatever you do, don't mess with Mjolnir. Thor's hammer is one of the most powerful weapons in the MCU, and it's capable of destroying an entire galaxy. Mjolnir can also reach Thor's hand even if he's on a different planet. In the movies, they only show a small part of the hammer's true potential.
Marvel Studios included Spider-man in Captain America: Civil War before receiving clearance from Sony to use the character. Had Sony denied their request, they didn't have a plan B, and the movie would've had to be re-written without Spider-Man.
When the MCU was created, the initial plan was for Agent Coulson to ONLY appear in the first Iron Man film. However, things changed when Nick Fury was dropped from Thor after contract disputes with Samuel L Jackson. So they decided to bring back Coulson to fill Fury's shoes.
After finding out that they would have to answer to a secret organization, the Pentagon decided that it would be best to stop cooperating with Marvel Studios. They didn't take kindly to playing second fiddle to S.H.I.E.L.D.
Believe it or not, everything that takes place in Thor, The Incredible Hulk, and Iron Man 2 is all in the space of one week. In the comics, this is referred to as Fury's Big Week. Within these seven days, Stark Expo exploded, Hulk smashed Harlem, Asgard was attacked, and a New Mexico was destroyed.
The answer to the age-old debate of who's the strongest Avenger is finally settled. After several failed attempts to design a character more powerful than Hulk, Stan Lee figured that the answer to his problems lies in Asgard. After all, the only thing stronger than the world's strongest man is a god.
Because of his checkered past, Robert Downey Jr. almost didn't get the role of Iron Man. Marvel directly told Jon Favreau that he shouldn't hire the actor under any circumstance. Fortunately, Downey pestered the movie's producers until they gave him a shot, and the rest is history.
Mark Ruffalo wanted to play the role of Bruce Banner in The Incredible Hulk, but Marvel rejected the idea. They believed that he wasn't right for the role, so they gave it to Edwin Norton instead. Ruffalo eventually got his dream part and has played the role of Bruce Banner in every Marvel movie since.
Before he was finally cast as Captain America, Chris Evans rejected two offers from the studio because he didn't feel it was the right part for him. Evans had concerns about the level of commitment needed for such a role, as well as the fame that comes with it.
There are two different infinity Gauntlets in the MCU. The first one is for the right-hand and appears in Odin's treasure room. The other one is for the left hand, and its the one Thanos removes from his vault at the end of Avengers: Age of Ultron and uses to fulfill his mission.
After the first Iron Man movie's success, the producers wanted to cut Terrence Howard's salary by $7 million and give it to Robert Downey Jr. The actor refused and quit the franchise. Don Cheadle then replaced him in what was then a very controversial move by Marvel Studios
The reason Captain America isn't seen enjoying shawarma with his fellow superheroes at the end of the first Avengers movie is that Chris Evans had grown a beard for his next project. Instead of asking him to shave it off for the scene, they instead gave the actor a prosthetic jaw to swear to cover his beard.
Thor: Ragnarok was renamed for the Japanese market. Over there, the movie was called Mighty Thor: Battle Royal, after a famous Japanese film and novel. The word "Ragnarok" isn't widely known in Japanese, so they decided to use a more familiar title.
After Tobey Maguire had suffered an injury while he was filming Spider-Man 2, the producers explored the possibility of giving the role of Peter Parker to Jake Gyllenhaal. However, Maguire recovered in time, and the idea was scrapped. Gyllenhaal would eventually enter the MCU years later as Spider-Man arch-nemesis, Mysterio.
Stan Lee has previously said that he wanted to play the role of Odin in the first Thor movie. This would have been Stan Lee's most significant role in the films to date. But unfortunately for him, the producers decided to give the part to Anthony Hopkins instead.
In the comics, the Maximoff twins have an unusually close relationship with one another. So when Pietro and Wanda Maximoff were first introduced in Avengers: Age of Ultron, the makers of the film toyed with the idea, but they didn't take it any further than that.
The Marvel Cinematic Universe is preparing to enter its second phase. They've already laid plans on how the next decade will shape up, and fans are eagerly waiting in anticipation. Although the recent passing of Chadwick Boseman may have set their goals back, it'll be interesting to see how the MCU honors its fallen hero in their upcoming movies.