While talking to EW, Whedon talked a little bit about The Avengers: Age of Ultron, and what differences we can expect from the comic book version of Ultron...
Whedon: “I knew right away what I wanted to do with him. He’s always trying to destroy the Avengers, goddamn it, he’s got a bee in his bonnet. He’s not a happy guy, which means he’s an interesting guy. He’s got pain. And the way that manifests is not going to be standard robot stuff. So we’ll take away some of those powers because at some point everybody becomes magic, and I already have someone who’s a witch.”
The "witch" he's referring to is the Scarlet Witch, Wanda Maximoff, a mutant sorceress gifted with chaos magic that allows her to basically do anything she wants. Because of a deal struck with 20th Century Fox, Whedon can use her even though she's also part of the X-men universe, but her mutant heritage can't be referenced at all. Elizabeth Olsen is said to be the frontrunner for the role right now, with Aaron Taylor-Johnson as her brother, Quicksilver.
As for Ultron, in the comics he was invented by Hank Pym, the Avenger known as Ant-Man and Giant Man. Pym implanted him with his own brain patterns, and when Ultron gains sentience he develops an irrational hatred towards his "father" and everything he loves. Built out of adamantium, he's virtually indestructible and has a number of powers ranging from super strength, speed, mind control, and more. He's a definite bad ass, and I can't wait to see what Whedon does with him.
The Avengers: Age of Ultron arrives on May 1st 2015.
