Originally Posted by Hawkingbird
Well, the fact that in X2 we see the names "Maximoff" on screen may answer the rights question
As explained by Kevin Feige
, Scarlet Witch and Quicksilver are a unique, special case in which both
Marvel and Fox have rights to Wanda and Pietro, with stipulations: Marvel cannot refer to their mutant origins/relationship to Magneto, and Fox cannot refer to their association to the Avengers.
So in theory, SW and QS could show up in both
an X-film and in the MCU, and possibly even be played by the same actors (though they'd have to have separate and non-conflicting contracts with each studio).
I think the Skrulls are the only other characters with a similar (but different) situation, where Fox specifically owns the rights to the original Super-Skrull and can probably use the Skrull Empire, while Marvel can only use generic Skrulls and the Skrull Empire as well. I don't know about the Super-Skrull that possesses the Avengers' powers.
Edit: Sam, I guess I took too long in looking for the original interview, haha.