I knew I needed Ben Burtt immediately, as soon as I got serious about it. I knew I needed to get a sound guy in right at the beginning of the production and I kept saying, "Like Ben Burtt, like Ben Burtt, like Ben Burtt, like R2, like R2, like R2." Fortunately Jim Morris, my producer, had just come over from ILM and he's got the golden rolodex and he just said, "Why don't we just get Ben Burtt to come over?" I'd never thought of it! He's sort-of like that about anyone I talk about...

The fun of being a sound designer is always to create a world of sound and, especially if it's a science-fiction movie, you get the challenge of really creating a whole world because most of the sounds you hear in the movie - from the ambiences, to the motors of the robots, to, in this film, the characters themselves - have to be created. You get to invent something that hasn't been heard before to some extent, it seems original, yet it has to be familiar enough that people know what it means. There's almost that contradiction in the challenge for sound.

When Ben came over I pitched him what was probably a half-assed version of the movie at that point, and I said to him, "I really need you to be 80% of the cast." I wouldn't blame him if he'd said, "I've spent twenty years of my life making robots, I'm not into it anymore." Fortunately I think he was seduced by the idea and the challenge of coming up with so many R2s and how to differentiate them. It really was a long process of discovery.

Andrew, in the very beginning, wanted to convince the audience that the characters of EVE and WALL-E were machines, so they had to sound like machines. It's not so difficult to, say, create a talking machine, but usually they're lifeless - there's no soul to it. It's a matter of coming up with a way of doing voices and collecting an array of sounds - of motors and other things - such that you give a character a sense of being alive; a soul, so to speak.

The clarity of ideas is the most important thing. When you have the challenge of animating a character that doesn't talk and is just expressing through sound effects, every move he does you really hammer into it and try to make the audience understand exactly what he's trying to do. All those little gestures and the moves with the head and the arms was so important because everything had to be really clear.

The end result is that it's exactly the film I wanted to make. I just closed my eyes and took a gamble and hoped that the rest of the world would want to see it as well, because I was just getting sick of everything and I just wanted something different. I think there's something underestimated about wonder. It's a hard thing to quantify, but to me that's the ingredient. If I look back at all of these movies that run an incredible gamut of genres and ratings, the ones that stick with me are the ones that tap into the wondrous response that I had either as a kid or a young adult. I think a lot of us here at Pixar are junkies for that - we want to recapture it for ourselves as much as our audience.

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