Josh Brolin has a multi-picture deal with Marvel which will see him doing the motion-capture as well as voice work for the Mad Titan Thanos, presumably through at least Avengers 3.
It's not been entirely clear until this point whether Brolin was doing all of the acting or just the voice; rumors swirled that his consultant, The Hobbit's Andy Serkis, may in fact have been doing the motion capture for the character, but both Serkis and Guardians of the Galaxy director James Gunn had denied that claim.
"We knew he was going to be in this movie. We wanted somebody to be more than just the voice," said Marvel Studios chief Kevin Feige in an interview at Collider. "Josh did the performance as well. We were looking at a wish list of, “Wouldn’t it be great if names,” and his name was on it. And you look at his face and the performances he gives, he could be Thanos without any effects. He has that kind of face and that kind of gravitas to it.
"We reached out to him and it was one of those things that does not happen all the time but when it does it’s very nice, where he was totally intrigued. He was a fan of what we did, he met with Jeremy Latcham in a hotel in London and learned about the characters a little bit. I spoke to him on the phone a few times. We ran it by James who loved it, ran it by Joss who loved it because Thanos is in this universe because of c. Then we shot him and recorded for it."
Guardians of the Galaxy, Brolin's first film in the Marvel Cinematic Universe, will be released on August 1.