Having featured in both the X-Men and Avengers comic books, Quicksilver and Scarlet Witch - the offspring of X-Men baddie Magneto - are the subject of a bizarre rights issue, whereby both Fox and Marvel Studios can use the characters as part of their respective worlds, although Marvel can't make reference to them being mutants (or Magento's kids) and Fox can't refer to them as part of Earth's Mightiest Heroes.
Considering the fact that X-Men: Days of Future Past has been filming for a while now, you can't help but think this is simply a knee-jerk reaction to the news that Marvel Studios were set to use the characters, and it would be a huge surprise if this didn't impact on Whedon's plans for The Avengers 2. Unless Fox and Marvel are set to combine their universes - which is HIGHLY unlikely - then I bet there's some pretty irate people at Marvel Studios at the moment. And I doubt Singer's tweet is going to calm anyone down either...
Before he was an #Avenger, he was just a REALLY fast kid. Thrilled to say #EvanPeters is joining #XMen #DaysOfFuturePast as #Quicksilver.
— Bryan Singer (@BryanSinger) May 23, 2013
X-Men: Days of Future Past is currently filming ahead of a release on July 18th 2014, with a cast that includes X-Men veterans James McAvoy and Patrick Stewart as Professor X, Hugh Jackman as Wolverine, Michael Fassbender and Ian McKellen as Magneto, Jennifer Lawrence as Mystique, Nicholas Hoult as Beast, Halle Berry as Storm, Shawn Ashmore as Iceman, Ellen Page as Kitty Pryde, Anna Paquin as Rogue and Daniel Cudmore as Colossus. Newcomers to the X-Men franchise include Peter Dinklage (Game of Thrones), Omar Sy (The Intouchables), Booboo Stewart (The Twilight Saga: Eclipse) and Fan Bingbing (Iron Man 3).
Meanwhile The Avengers 2 is expected to reunite the likes of Robert Downey Jr. (Iron Man), Chris Hemsworth (Thor), Chris Evans (Captain America), Mark Ruffalo (The Incredible Hulk), Jeremy Renner (Hawkeye) and Scarlett Johansson (Black Widow), and is due to arrive in cinemas on May 1st, 2015.