TORONTO—For most 13-year-old boys, having Aragorn from The Lord of the Rings play your dad in the epic science-fiction movie The Road would be a dream come true, but Kodi Smit-McPhee may be one of the few kids on the planet who didn't know anything about Viggo Mortensen until recently.

“I'm not a big fan of fantasy stuff,” Smit-McPhee tells the Georgia Straight. “Still haven't seen it.” But he says his father was really impressed.

A moment later, Mortensen strides into the hotel room, but he tries to keep the focus on his young costar: “Continue. He's smarter than me anyway.”

The Australian actor smiles and talks about meeting Mortensen in Los Angeles for the final audition. Mortensen chimes in. “I knew that the most crucial and most difficult part of casting, where we'd need luck and skill from the director and the casting director, was finding the Boy.” The Boy is the name of Smit-McPhee's character in Cormac McCarthy's dystopian novel about two of the last survivors on a postapocalyptic Earth so bleak it makes Mad Max look like Mardi Gras. “Without the Boy breaking your heart in the book, the book doesn't get to you the way it does. And I knew that if we didn't find a great, great young actor, we were lost.

“I got to read with the four finalists, and I have to say that all four of them would have done a great job,” Mortensen says. “The other three—one was from Ontario, two were from the United States, and Kodi from Australia—there was something. He had something extra. An extra sort of wisdom, presence, and, most importantly, I could feel it too. As much as I liked the others, I felt a stronger connection with him.”

And that connection is vital because, although there are other actors in the film (opening Friday [November 27])—including Oscar winners Charlize Theron as Wife and Robert Duvall as Old Man—it is essentially about a father and son trying to survive in a world where everyone you meet is potentially eyeing you as their next meal.

“If I have an emotional scene, it's most likely an emotional scene that's connected to Kodi directly, and we just had to be there for each other, and that brings you together,” Mortensen says. “It's like anybody, I suppose, on a sports team or going through really inclement weather together, or a natural catastrophe, or war, or anybody who has a friend in common who's suffering or dies, or a family member. What we had to do emotionally pushed us closer.”

Asked about shooting so many scenes together, Mortensen turns to Smit-McPhee, grins, and says, “It was fun when someone else would show up, wasn't it?” “Like Robert,” Smit-McPhee says with a smile. “Robert Duvall, yeah,” Mortensen clarifies.

Smit-McPhee adds, “And Garret. Garret was really nice.”

Mortensen continues, “Yeah, Dillahunt, who played the road-gang member. He's a very good actor. He was scary and creepy, wasn't he? The way he looked at you, he looked like he was already imagining your barbecue: 'That boy looks like good eatin'.' ”

The two laugh, and Smit-McPhee adds, “He had shark eyes—he had these, like, black eye thingies. They were weird.” Mortensen agrees, “Yeah, they made his eyes even more scary.”

Mortensen says that before shooting, he and Smit-McPhee explored Pittsburgh—where the film was shot—in order to build their friendship.

“I love Pittsburgh,” Smit-McPhee says. “It was fun,” Mortensen adds. “We really had fun there. We walked around a lot, learned things together, and Kodi's dad was there—Andy McPhee. He's an actor also, and he understood the process. And during the day, we'd get together with the director [John Hillcoat] and the writer [Joe Penhall] and we'd work on what the ideas were behind certain scenes and talk things through so we could get all of us on the same page before shooting, which would save time and avoid as much confusion as possible.”

In a separate interview with the Georgia Straight, Hillcoat mentions that besides the fact that Mortensen looks like he could survive a journey through, well, Mordor, the fact that Mortensen is a father (of a 21-year-old son) made him feel even better about casting him in the role.

Mortensen agrees that being a real-life dad helped him bond with Smit-McPhee, but he says it also helped build his connection with both Hillcoat (a new dad) and the novel's author, McCarthy—with whom he spoke before they started filming. “I had my book full of notes and all that stuff, and we didn't talk about it. We just talked about his kid and my kid, and being dads. And that was it. And that was all I needed.”