Andy Serkis teamed up with Joss Whedon's Avengers 2 to flesh out more than just the Hulk.

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Well known for his work as Gollum in The Lord of the Rings and The Hobbit trilogies, Serkis is at the front lines of motion capture technology. The upcoming Marvel film employed the expert to know only update Mark Ruffalo's Hulk, but also to help create Age of Ultron's title character.

Now that fans have seen the villain in action, it's time to jump behind the scenes.

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"We did some work on Ultron, on the development of Ultron before James Spader came on board," Serkis told Empire (via MovieWeb). "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."

The final version, which you can see in the trailer below, gives an interesting cross between a human and the cold, stop-and-go motions of a robot.

Find out more when The Avengers: Age of Ultron enters theaters on May 1.