I found this awesome interview. Goes into the thought process of crafting the story for Toy Story 3.
On speaking to adults and kids at the same time
Michael Arndt: "Your first concern when you take this over is you're just trying to make it all fit together on a basic narrative level. ... We did 60 different drafts of the scene before we got to the final version. ... It was really only after we set up the narrative structure of [toys realizing they're going to serve their careers being played with by children and then 'retire' to the attic] that we realized how emotional it was, and how much it played into people's fears of obsolescence. ... I think everybody feels the way these toys feel — like they've given themselves over to this child, Andy, and given him 100 percent and played with him and given him so much of their lives, and now he's going away. And they don't [really] want to go with him to college; what they really want is acknowledgment, and I think that's a universal thing. I think a lot of people go through life feeling like they work really hard and they're doing a good job and they just want some sort of emotional acknowledgment."
On writing animated features vs. nonanimated features
Arndt: "You can't make any distinction between a live-action character and an animated character. They're all real characters. To me, Buzz Lightyear is as real as Olive Hoover [from Little Miss Sunshine] is. You want to take their problems as seriously as they take them themselves, and you want to be as emotionally honest and intelligent about what they're going through as you can possibly be. But it does put you in these sort of odd situations when you're a writer and suddenly you have to think, 'OK. I'm a little rag doll and I've just been put into a knapsack,' or, 'I'm Mr. Potato Head and I've just lost my parts. How do I feel about that?' There were times when I thought it was funny to be writing scenes like that, but you have to take it seriously. You have to put yourself in that position and think, 'What would I do if I were in that situation?' "
Arndt: "The great thing about animation is you get to see these actors record their lines ... and that does inform how you think and write about the characters. So you can add parts of Tom Hanks' personality or Tim Allen's personality or Don Rickles' personality to the characters. It creates this feedback loop in animation. You get to go watch the actors perform, and then you can go back and write a little bit more incorporating what they've done and then you can record them again."
On writing for toys
Arndt: "When we're in a story meeting and we're trying to figure this stuff out, we usually go to the human analogue. We don't talk about, 'Well, if I were a rag doll,' or, 'If I were a plastic dinosaur,' because you want to get to the emotional truth of this story, and you want to get to the emotional truth of these characters. So you say 'OK. Woody: He's a little bit like a helicopter mom. He's a little bit like a mom who can't let go of her child.' So we always try and figure out the human equivalent of these characters."
Lee Unkrich: "But then the fun thing is, once we have that figured out, we try to figure out ways to make their issues particularly a toy's issue. I mean, Ken [of Ken and Barbie] was a great [example], and we made endless fun of Ken. Ken is a whipping boy. We thought, 'What is it like to be a guy who is a girl's toy?' You're a guy, but you're only played with by little girls. And further, he's just an accessory for Barbie. He doesn't carry equal weight to Barbie. He's really no more important than a pair of shoes or a purse or a belt to her, and we knew that he would have to have a complex."
Arndt: "You go, 'What are going to be the issues of a character like Ken?' What's going to be the stuff that keeps him awake at night? So immediately, you go, 'Maybe he's a bit insecure about the fact that really he's a girl's toy. Maybe he's in denial of that. And then this whole sort of richness opens up."