No, says Chris Buck, with the sunniness of a man just back at work from a Balinese holiday, he's not sick of Let It Go. He still gets sent videos of excited punters singing their own versions of Frozen's title track and he loves it: "That Let It Go means so much to so many people, I kinda embrace that."

Buck, a career Disney animator with various roles on films such as Pocahontas, Who Framed Roger Rabbit? and Surf's Up! on his CV, directed the 2013 hit which two years on, still obsesses little girls the world over. Even he's not sure why. "It's really hard to analyse why this movie tapped into something that not all our movies do. I've worked on quite a few and never experienced anything like this." After a pause for thought, he wonders if because there's something for everyone: romance, warmth, music, humour. "It's a dream come true to work on a movie that got that response.

"You hope, even from the beginning that it can be something special and along the way I saw images, even early on, that made me think this could be really, really spectacular. I got glimpses into the special moments the movie could have, but it was not until we had a viewing with an audience in June 2013 that I thought about what was about to happen."

At that stage, the movie was only about 50 per cent animated, and already bucking the animated-movie trend of what Buck calls 'fail and fail early', and his team being prepared to change their view of what a movie could be, right until the last. "We keep revising as we go, revising, revising, and we don't put anything in animation until we feel it is really ready," he says.

Buck was in the same class at the Califonia Institute of Arts as Pixar boss John Lasseter and director Tim Burton and then a decade later, returned there to teach night classes. Among his students was Pete Docter, who would go on to direct Up and Inside Out. "He was such an amazing talent … I just knew there was something really special about Pete. I knew he'd go on to do great things. Pete's movies are so personal: you could show me Inside Out and if it didn't have his name on it, I'd know it was a Pete Docter movie. I was honoured to teach him: I don't know if I taught him, or he taught me more." It is, he says, a tight community and rather than being competitive, they celebrate each others achievements.

Buck had arrived at Disney just as hand-drawn animation was being replaced by computer-generated imagery (CGI). The artform hasn't changed, he says – it's still all about the story. He remembers the release of the CGI trailblazer, Toy Story, in 1995 (he was working on Pocohontas at the time) and his excitement to see it. "But yet again, they were telling a great story, just with new toys." But the possibilities it offered, he says, had even the oldest veterans exercised: two of Walt Disney's original 'nine old men' were still at the studio and they were just as excited, he says. But then again, "Walt himself was always pushing to do new and innovative things."

Now Buck, at 54, is the older generation. His sons are 18 and 22 (his oldest died in a car accident just before Frozen's release), giving him some insight, he pleads, but really, "we're all kids at heart. Just a bunch of big kids who love making movies and telling stories. That childlike innocence wil always be there, no matter how old I get."

And so a Frozen sequel is planned. There is, Buck concedes, some pressure to deliver. "We try not to think about that."

Frozen, he says, hasn't changed his life. "I still love what I do, I still love working at a studio." But when he was in Bali, he visited some schools and everywhere he went, he saw Frozen merchandise and the kids knew the film. "I guess all these movies have a worldwide impact, but this one is the one I've been connected to closely, I guess its overwhelming."

And he truly believes his movie, and the others in the genre, are a force for good. "I am happy and proud to be part of that. I don't take lightly the power that these movies have, and when kids watch them and watch them over and over and over, so we try to put positive messages in the movie that will make this generation better for it."