Andy Serkis, known for motion-capture work with Gollum on Lord of The Rings and portraying Caesar in the new Planet of the Apes movies, is also working on The Avengers 2.
Mark Ruffalo took to his Twitter to offer up a Hulk tidbit to a fan.
Ruffalo was asked if there was something he could say about the Hulk in The Avengers 2, with Ruffalo replying, "Well, I have been working with the great Andy Serkis on the big green boy and he is going to be even better then A1."
For the Hulk, Ruffalo wears a mo-cap suit which records his movements with the Hulk added in digitally.
Here's an image and video from The Avengers: