Six years after it opened, how do you explain the enduring appeal of "Toy Story"?

We wanted to tell a good story, first and foremost, because we knew that's what audiences like - a good story and characters. Technique and technology doesn't entertain audiences, it's just what you do with it. We just made a movie we would like to see. We didn't want to do what was being done in animation, so we chose the buddy picture as the form. One of the things I love about the buddy picture is that, by nature, the stories are about characters that grow. When you can have a character that the audience likes from the beginning, but then you put them in a situation where they grow - I think that gives it a lot of heart. And that's where a lot of the enduring appeal is.

The film's become a phenomenon, though, even spawning a "Toy Story on Ice" show...

I've become friends with the toy maker who made the original Buzz Lightyear and the Woody doll, and he has never stopped making them. I think he's up to 25 million combined pieces! That's unbelievable, and he keeps making them. He's like, "It's a whole new generation now." And that was partly in the back of my head: that if you do animation right, it can live a long time. You look at the classic Disney films... what other movie from 1938 does the world watch as much as "Snow White"?

You must have had doubts about it all, though, being pioneers of this new technology?

Well, actually I didn't have that many doubts. Others had doubts. When we were making "Toy Story", there were a lot of people saying, "I don't know if people can sit still for an hour and a half of computer animation." But we never did. We had faith that we were telling a good story. And we also put our own - you might say geeky - interests into it, because I just love toys. I think being an animator, you have to be a bit of kid who's never grown up. I have a big toy collection, so there's this love of the subject matter that we were telling.

Is that why you set your movie in this toy world?

I think the subject matter lends itself to the medium very much. When we started "Toy Story" back in 1991, computer graphics tended to make everything look like they were made of plastic, and so it was a natural subject matter. But with computer animation, we were also able to get the detail: the seams on Buzz Lightyear - the little screwheads holding the parts together. There was an embossed '© Disney' on his butt. All those things made it feel like the audience was looking at it going, "Yeah, I believe those are toys."

"Toy Story" receives its terrestrial television debut on BBC1 on Christmas Day, 4.40pm.