Geoffrey Rush gushes over Quebec child co-star Sophie Nelisse

Sophie Nelisse holds the award for Actress in a Supoorting Role for the movie "Monsieur Lazhar" at the 32nd Genie Awards in Toronto on Thursday March 8, 2012. THE CANADIAN PRESS/Chris Young.

TORONTO -- Oscar-winning actor Geoffrey Rush jokes he was worried about being seen as an "old hack" next to his young Canadian co-star in "The Book Thief," opening Friday.

"The King's Speech" star plays kind-hearted adoptive father Hans Hubermann in the big screen adaptation of Markus Zusak's young adult bestseller, while Quebec actress Sophie Nelisse is his spunky ward, Liesel Meminger.

"She was just amazing to work with," Rush gushed as the two discussed the film side-by-side during a recent visit to Toronto, with Rush praising Nelisse's ability to deftly handle the film's more emotional moments.

"She could go into that zone and then I liked that she could find levity and some fun and do her schoolwork (at the same time)."

At 13, Nelisse admits she's already pretty committed to building a long-term career as an actress.

The chatty performer says she even put aside her beloved gymnastics -- dropping a long-held dream to go to the Olympics -- in order to take this role as a German girl fascinated with the power of words in the lead-up to the Second World War.

But it wasn't an easy decision, she allows, noting she still wasn't sure about her choice even as she pursued the part.

"Even when I first started to audition I was like, 'I'm still not sure if I want the part, if I want to audition,"' says Nelisse.

"But then I read the script and it's the first time a script made me cry. I was like, 'You know, it has to be good if it made me cry.' And then when I got the part I said, 'Yes,' because I just think there's more advantage in acting than in (gymnastics). I mean, there's so much sacrifice you have to do in gymnastics to maybe achieve your goal. I think maybe I'll go into acting, it's easier."

Nelisse has already achieved a fair amount of success with just a handful of films.

Her turn in "The Book Thief" brought her a spotlight award at the Hollywood Film Awards last month, where she was among three emerging talents deemed ones to watch.

She catapulted to fame two years ago as a mature latch-key kid obsessed with death in the Quebec tear-jerker "Monsieur Lazhar," which competed for an Oscar last year in the best foreign-language film category.

Rush says he was blown away by Nelisse's performance in that film, about an Algerian immigrant who helps a class of Montreal students grapple with the sudden death of their teacher. He says he sees some common elements between that Canadian hit and "The Book Thief."

"They don't pussyfoot around to play down to children," says Rush, noting that "The Book Thief" director Brian Percival was keen on keeping performances honest.

"Brian was a great guide because he said: 'No melodrama, no sentimentality.' I remember when we were shooting (one) scene he said, 'Geoffrey just tell her what she needs to know. There's a seriousness and an emergency and an imperative time frame and you've got to balance (feelings of), "I don't want to freak her out" but "I've got to tell her the nuts-and-bolts of it."'

"And of course Sophie's there responding and I could just feel her absorbing it as if she'd never heard those words before. Great actress."

Nelisse stars as the war-scarred Liesel, who is sent at age 10 to live with Hubermann and his stern wife Rosa, played by Emily Watson, as the Nazi Party increasingly asserts its presence on the streets of their small German town.

Percival says he was "desperate to make the film" after reading the script in one sitting following a long day shooting his other period saga, TV's "Downton Abbey."

Seated alongside Rush and Nelisse for a day of interviews, the British director says he was attracted to the script's unique portrayal of death -- which also appears as narrator here, as Death does in the book -- and the fact it centres on the rarely depicted experiences of average Germans during the war.

"There was this fascist ideology that came along and if you didn't believe in this you were going to have a pretty rough ride, you could well be locked up and turned away. So a lot of people didn't believe in it but they had to go along with it because they wanted to protect the families, protect the children," says Percival, whose father served in the Royal Air Force during the war.

"There were a lot of people that did believe in it and we tried to get that balance in the film.... We see these ordinary folk ... in the bomb shelter terrified by bombs falling around them and then the following day we see them berating a Jewish character that is being taken off to a camp."

Rush says no one had ever offered him a role like Hans Hubermann before, describing the man as "a simple, unadorned ... working class guy.

"I think he's got a fairly interesting inner life going on but he's not as eccentric or as flamboyant as a lot of other things that have been on my own particular CV, if you know what I mean," says Rush, who played Captain Hector Barbossa in the "Pirates of the Caribbean" franchise, Leon Trotsky in "Frida," The Marquis de Sade in "Quills" and genius pianist David Helfgott in "Shine," for which he won an Oscar.

"It just felt like a nice challenge to do something a bit more minimalist."

However, Rush and the rest of the cast and crew certainly didn't hold back for one special day on set, when Nelisse turned 13 years old.

Nelisse says she was stunned by a surprise party that erupted during what initially seemed like an ordinary day at work.

"They said, 'OK, we're just going to do this scene again for safety' and Geoffrey was not in the scene but he came," recalls Nelisse.

"(I said) 'What is he doing there? Oh my God, what is he doing there?' And then he was there with the gifts and there were around 500 extras and they all started to sing, 'Happy Birthday.' I was so embarrassed. And they were filming it. And it was just so much fun."

"I can imagine you going, 'He's so unprofessional. What's he doing?"' Rush jumps in, with mock indignation.

While in Toronto, Rush says he dined with "The Drowsy Chaperone" scribes Don McKellar and Bob Martin to hash out ongoing plans to bring the Broadway smash to the big screen.

He says McKellar and Martin, who won Tony Awards for writing the musical's book, have written "a fantastic script."

"They've found a great film language for it and we've now got a script, we've got a document we can start handing out to actors that we think would be great to play the roles," says Rush, tabbed to play Man in Chair after tackling the role in the Australian version of the musical.

"It's still this beautiful sad geek wanting to share this obscure Broadway cast recording with the audience and they all find out that they love it. And it's as funny as all get out."