Before the MCU became a blockbuster monster, the studio was a lot more open to sharing their universe with the rest of Marvel's heroes at rival studios. It's long been rumored that Marvel had considered having Hugh Jackman appear as his immortal clawed soldier alongside Cap during World War 2. Even if rights meant he couldn't be CALLED Wolverine, it still would have been an incredible cameo.
Casting Iron Man
He may have become the face of the Marvel Universe, but when the role of Iron Man was being cast, the studio couldn't have been less convinced Robert Downey Jr. was their man. While they would still have preferred Tom Cruise, director Jon Favreau knew Downey could pull off a brilliant man who realizes he'd been wasting his life - since he already had himself.
After years playing the voice of Tony Stark's AI JARVIS, fans finally got to see actor Paul Bettany on screen, as the new Avenger, Vision. But it was a first for his costars, too. The actor admitted that he had never worked with Robert Downey Jr before then, having spent close to a decade just recording his lines in a studio after filming had wrapped.
Iron Man’s Suit
It seems like a dream come true to wear the Iron Man armor, but the reality of a suit of armor isn't as glamorous. Thanks to advances in CG, Robert Downey Jr. only has to wear a headpiece or shoulder pads on set. Whenever the iron Avenger's face isn't visible, fans are actually watching a digital creation, or a stunt man. Sorry to burst the bubble.
It's an ironclad rule that no actor can play two different characters in the MCU, with Paul Bettany's shift from JARVIS to Vision the only exception. Well, unless you count actress Laura Haddock, who appears in Captain America looking for an autograph... and again, as Peter Quill's dying mother. The studio has denied any connection between the roles, making her casting... impossible to explain.
Guardians On A Budget
Guardians of the Galaxy turned out to be one of Marvel's biggest hits - but they didn't expect it to be. In fact, the studio only agreed to pay for the movie's massive prison set to be built once a plan was set to melt down the steel after filming wrapped, so it could be sold for scrap to gain back the money spent. We doubt that will be a problem for the sequel.
These days, almost every young actor is fighting to play a superhero and hit blockbuster level. But when Marvel sought out actor Chris Evans to play Captain America, he wasn't sold. With terrible memories of his Fantastic Four contract, Evans actually turned Marvel down - THREE times. He finally agreed when Marvel dropped his initial contract from 9 movies to 6, and the rest is history.