(CBR) What’s Andy Serkis doing on the set of "The Avengers: Age of Ultron"? Aside from helping Mark Ruffalo embrace his inner Hulk, that is. We already know Serkis and his Imaginarium Studios have been hired to assist Ruffalo in bringing the Jade Giant to life for round two of the Marvel franchise.

But Serkis also has a role to play in the film, and no one is willing to reveal who it is. Serkis, however, has at least confirmed who he’s not playing: Thanos, the Mad Titan teased at the end of "The Avengers," and featured in the upcoming "Guardians of the Galaxy."

“I’d have to deny that character at this point,” the actor told The Daily Beast. “But I am playing a character. I was really thrilled that Joss Whedon asked me to be involved. It’s fantastic. I’ve had a ball working with them, both as performance capture consultant through the Imaginarium, but also being asked to be in it. But I can’t say anything more!”

It’s been reported that Josh Brolin will provide the voice of Thanos in the Marvel movies, but that hasn’t been confirmed; it’s also possible another actor is doing motion-capture work for the character. But it won’t be Serkis, based on his comments.

While he’s not talking much about his role in "Age of Ultron," Serkis is much more willing to discuss the tools he and his colleagues are providing Ruffalo in order to create a new kind of Hulk.

“Previously, he would’ve walked onto a set and you’ve got Thor and all the other characters in their costumes looking magnificent, and then you’d have Mark in a gray motion-capture suit playing this enormous character, so it’s about giving the actor the right atmosphere and credibility for the performance, which we did in a number of ways,” he said. “We had to educate the director that the actor owns the role, and what you get on the set is what you should be aiming to put into your cut as the final performance — with the rendering coming later on.”

"The Avengers: Age of Ultron" assembles on May 1, 2015.

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