When the Trolls filmmakers managed to get Anna Kendrick and Justin Timberlake to voice the lead characters Poppy and Branch in what would become a riotous musical comedy, cleverly titled Trolls. Kendrick admits that she was intrigued when she first heard about it. "I had trolls growing up," she says. "I had the pencil toppers, which made it seem like homework was fun, even when homework wasn't fun. They are that kind of ugly-cute. So my first question to them after they finished pitching me the movie was, 'Does Poppy have a diamond belly button?' Because the jewelled belly button trolls are the best trolls. They said, 'No, but she has glitter freckles!' So I was like, okay, that's fine."

Anna Kendrick and Justin Timberlake provide the voice overs for TrollsAnna Kendrick and Justin Timberlake provide the voice overs for Trolls

In voicing the character, Kendrick says she kept the image of Poppy in her mind the whole time. "I just love that she is tiny and she has pink hair and she loves parties," she says. "But she's also on this adventure to save her friends. Nobody else in the troll world is brave enough to go, and she's the one who goes after her friends. She even has a song to psych herself up and be brave and be courageous while being tiny and pink."

Timberlake found it a bit strange to see some of his own facial tics replicated in Branch. "They shoot your face when you're in the sound booth, so they use that to animate the mouth of the troll," he says, admitting that creating a character in short recording sessions was tricky. "Because you do everything in such bits, you don't get to see how it works together. But because of how hilariously optimistic Anna made her character, it was actually funnier the more ornery I was. So when I did get to see it put together, I was like, 'Oh okay, I get it.'"

And then there was the added responsibility of producing the music. "To take these classic toys and really modernise them, that was our MO with the music as well," Timberlake says. "Some 7-year-old will walk away knowing The Sound of Silence, which is very cool, and a song like True Colours. And then I also wrote four original songs. I got to see some of the animation they were working on, so the music definitely has a '70s funk feel. That was definitely an inspiration for Can't Stop the Feeling."

Watch the trailer for Trolls: