You may have noticed that there are two different actors playing Quicksilver in upcoming “X-Men: Days of Future Past” and “Avengers: Age of Ultron”. Marvel is known for holding on very tightly to the rights for their superheroes, yet with Quicksilver seems to be a little confusing to us general folk.
Why can’t the same actor play in X-Men and in Avengers? The answer needs an explanation first:
Marvel owns the right to every Marvel Superhero, and production houses like Universal, 20th Century Fox, Paramount and Disney buy these right from Marvel. These rights give them a indefinite access, a 3 movie deal, or a one movie deal in which they can depict the superhero according to certain criteria set by Marvel.
Fox owns the film and TV (non-animation) rights to all the Marvel characters deemed to be mutants (which include Quicksilver). Marvel retains the movie and TV (non-animation) rights to the Avengers characters (Which also includes Quicksilver). Yet, some of The Avengers are mutants. This is the reason why we have a Fox movie (X-Men) and a Marvel movie (Avengers) wanting to use the same characters in it. It’s tricky business that some entertainment lawyers who drive super nice cars are paid a lot of money to hash out. Screenrant has a pretty comprehensive list on which production company owns which marvel characters.
Bryan Singer cast Evan Peters as Quicksilver for “X-Men: Days Of Future Past”. He’s shooting first, so presumably, he will win the showdown in terms of being the first to define the character on film.
Josh Whedon cast Aaron Johnson as Quicksilver for “Avengers: Age of Ultron”, but he has larger plans for the character, though, and wants to use him for more than just one action sequence.
The way the arrangement works, Marvel Studios (Avengers) cannot refer to the Quicksilver as a “mutant,” and they can’t mention Magneto at all (His Father). Likewise, Fox can’t make any reference to The Avengers in their film. This means they’ll have to either explain his powers in a different way in “The Avengers: Age of Ultron”, or they’ll just have to make no mention of his origin at all.
There you have it. Makes sense right?