Performance-capture expert Andy Serkis was involved with the movement of both the Hulk and Ultron in The Avengers 2, as well as has a mysterious role (speculated to be Ulysses Klaw and having a connection to Black Panther).
Serkis spoke with Empire about working with the pair.
"We did some work on Ultron,” Serkis said. “On the development of Ultron before James Spader came on board. In terms of movement styles: Was he gonna be human-like? Was he going to be robot-like? So we worked with a bunch of different people, from body-popping experts to dancers, to this guy called Neil who’s nearly eight feet tall...
“We gave Mark weights, we had voice projections so he could do his Hulk roar,” Serkis explained. “On screen we could have a virtual representation of the low-res avatar of The Hulk, so he could come out and feel that sense of scale.”
"The Avengers: Age Of Ultron" hits May 1, 2015 directed by Joss Whedon starring Robert Downey Jr., Chris Evans, Chris Hemsworth, Scarlett Johansson, Mark Ruffalo, Jeremy Renner, Samuel L. Jackson, Elizabeth Olsen as Scarlet Witch, Aaron Taylor-Johnson as Quicksilver, Paul Bettany as Vision, with James Spader as Ultron.
The Avengers: Age Of Ultron extended trailer:
When Tony Stark tries to jumpstart a dormant peacekeeping program, things go awry and Earth’s Mightiest Heroes, including Iron Man, Captain America, Thor, The Incredible Hulk, Black Widow and Hawkeye, are put to the ultimate test as the fate of the planet hangs in the balance. As the villainous Ultron emerges, it is up to The Avengers to stop him from enacting his terrible plans, and soon uneasy alliances and unexpected action pave the way for an epic and unique global adventure.