When you've been responsible for the most successful animated film in history and you get the go-ahead to make a sequel it's kind of a mixed blessing.

You know that on the back of the first one there's a Broadway show in the works, there are theme rides and pyjamas and pencil cases, action figures and, above all, untold dollars flowing into the Disney coffers. And somehow, you're going to try and do it all again.

"Now I'm terrified," jokes Chris Buck – the co-director, with Jennifer Lee, of Frozen, the short film Frozen Fever, and the recently announced Frozen sequel, when I mention the weight of expectation. "That's the first I've ever thought of it. Maybe I should say no."

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The sequel is as yet untitled and undated but far from unexpected. Frozen has been the sort of pop-cultural phenomenon a studio can only dream of. And then dream of again.

Frozen co-director Chris Buck: 'There's a lot of pressure.' Photo: Matt Streatfield

It took US$1.27 billion at the cinema worldwide and another US$308 million in the US alone from home entertainment (Blu-ray, DVD and digital downloads) – and that's despite being illegally downloaded almost 30 million times in 2014. Not to mention the countless renditions by besotted 5-year-old girls of Let It Go – many of them horrendously off-key, though sort-of charming in their own way. The first time, at least.

Buck admits that wrestling with the idea of trying to match that success is part of the reason it took so long to announce a sequel.

"How do we live up to the phenomenon of the first one? There's a lot of pressure. And we'll put that on ourselves too; we'll be very demanding about how good this one has to be."

Buck was in Australia last week to deliver a talk in Newcastle on his career to date. "I call it 'No Regrets'," he says. "It's about the ups and downs of a creative career."

He's had his share of both, starting as an intern animator at Disney in 1978, rising through the ranks to direct The Fox and The Hound and become head of animation on Pocahontas​, and leave in 2004 as the studio lost faith in hand-drawn animation but struggled to embrace the computer era.

It must have been devastating, to see the craft that had built the studio dismissed in that way.

"Oh, absolutely," he says. "It was very hard to see. I was very depressed. I'd grown up in it, we'd had the torch handed down to us by Walt's favourite animators, the guys he called his nine old men."

But the old animators weren't crushed by the advent of the computer. "They were thrilled. Some of them were still around to see Toy Story and they were excited. They said Walt would have done the same thing. If the technology had been there, he'd have found a way to do the first computer-animated film."

And, no doubt, he'd have found a way to follow it with an equally successful sequel.

Buck says he doesn't know what the story will be yet – "we're still doing a lot of research," he says, "we have some ideas and we're excited about where the story's going" – but he's fully alive to the responsibility that rests on his and Lee's shoulders to get it right. And not just for the bean counters, either.

"I'm aware, with each movie I do, how it's going to affect people, especially young people. They don't just watch it once – they watch it over and over again. So whatever message it is, whatever the theme, I always feel it has to be positive and empowering."

Building an animated film takes about four years, he says, though "it's a bit different with a sequel because we have some of the characters and locations built, so maybe a little bit less". Whatever the time frame, it seems he is destined to be snap-frozen in that icy realm for a good while yet.

"When we were making the short I joked that it wasn't Frozen Fever it was Frozen Forever," he says. "Luckily everybody likes the world and the characters."