How are two different studios able to use the same Marvel character? Marvel Studios President Kevin Feige told SuperHeroHype how it works, last May. Speaking of both Pietro "Quicksilver" Maximoff and his sister, Wanda "The Scarlet Witch" Maximoff, who are both mutants, he discussed how Marvel Studios and Fox could use both characters.
We both [studios] have them [Quicksilver and The Scarlet Witch]. There's a specific arrangement with those two characters that would allow us to use them with "Avengers," but not discuss or reference their mutant or Magneto-related lineage. They can use them as mutants and as Magneto's relatives [they are twins, and his children], but cannot have anything to do with "The Avengers."Like DC Comics' Flash, Quicksilver possesses super-speed, but his top velocity is nowhere near that of DC's Scarlet Speedster. The Flash, using the Speed Force, can run at speeds approaching or even exceeding light speed, while Quicksilver is relegated to speeds up to Mach 10.
Quicksilver's sister, Wanda Maximoff (aka The Scarlet Witch), is also going to be featured in the "Avengers" sequel. Elizabeth Olsen is rumored to have been cast in the role, with Samuel L. Jackson (Nick Fury) telling the Wall Street Journal that the role is hers, but with no official studio confirmation.