'Walter Mitty's' Ben Stiller and Kristen Wiig Talk Tackling Movie's More Serious Tone (Video)

The actor-director also discusses helping to craft the soundtrack and provides an update on the highly anticipated "Zoolander" sequel.

Although The Secret Life of Walter Mitty has some funny moments, it's less of a broad comedy than many of the movies actor-director Ben Stiller and co-star Kristen Wiig have done in the past.

In the film, Wiig plays a fairly serious role as Stiller's character's co-worker and love interest. The actress tells The Hollywood Reporter that the more subtle, quiet part was somewhat difficult for her.

"It was a challenge for me in the beginning because I'd never done anything like that before," she says.

But she explains that she likes doing dramatic roles as well as comedic ones because they exercise different muscles.

REVIEW: The Secret Life of Walter Mitty

Stiller, who stars in and directed the film, didn't seem challenged by trying to maintain a balance between the movie's funny moments and its more emotional scenes.

"You don't really delineate when you're making the movie, you just sort of do the scene. And wherever it's at in the script, the humor or the emotion is going to come out of just playing the scene in a real way," he tells THR. "You always have a sense of something, if it's funny or serious, and I think that informs what you're doing, but I don't try to play it differently, necessarily, I just try to play it as honestly as possible."

The tone of the movie also is shaped by the music Stiller used, including songs by Arcade Fire and Of Monsters and Men, scenes involving David Bowie's "Space Oddity" and "The Pina Colada Song," compositions by Jose Gonzalez and the score by Teddy Shapiro.

"It all comes out of trying to get the feeling, and for me that came out of first the theme that Teddy Shapiro wrote and then asking Jose Gonzalez to come and look at the movie and collaborate with Teddy and put his voice on the soundtrack. That was really important and the evolution of all that over the course of editing the movie … we went through a lot of different versions of all the music and tried to winnow it down so we got as cohesive a tone to it as possible while still keeping in certain songs we just liked because we just thought they worked well," Stiller explains.

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The actor-director had a far less detailed response when we asked him about the status of the much-anticipated Zoolander sequel, which has been in development for a few years and has a script. There hasn't been much movement on it lately despite a clearly expressed hunger for a follow-up among fans of the original film.

Stiller noted that the film "hasn't come together yet," adding, "we have a script that I think we like, but I'm not sure what's going to happen with it."

However, he indicated that he wants to take his time with the sequel to make sure that it lives up to fans' expectations.

"I feel like the audience for the original movie -- the fans of the original -- I want to make sure that the movie lives up to it," he says.

The Secret Life of Walter Mitty hits theaters Christmas Day.

Watch THR's video interview with Stiller and Wiig above.