Irish actor Michael Fassbender had to brush up on his German for his role as a British-film-critic-turned-spy in Quentin Tarantino’s “Inglourious Basterds.”

Fassbender, who was born in Germany, but raised in Killarney, County Kerry, says his accent is naturally confusing, so putting on an authentic German accent was a challenge.

The actor, who played up his Irishness in his starring role as IRA hunger striker Bobby Sands in the critically acclaimed film “Hunger,” says, "People say [my accent] sounds a bit Canadian really," he said. "It's a sort of strange mid-Atlantic, I suppose."

Fassbender’s father is German, while his mother is Irish. He was born in Germany, but his parents “wanted to raise a family in a green environment and open spaces so we ended up in Killarney,” where he picked up an Irish lilt.

Fassbender gets in touch with his German roots in Tarantino’s film during a scene where his character, Lt. Archie Hicox, an undercover British agent posing as a German officer, gets caught in a full German dialogue with an actual Nazi major.

Fassbender, who has been lauded by the New York Times for his role in the film, had to carry on an authentic German accent in the tense conversation that lasts for about 20 minutes.

"I can chat in German and watch a film in German, but my spoken German is rusty," the Irish actor said, so to avoid speaking German with an English accent, he worked with a vocal coach to prepare for the role.

"Certain vowel sounds would be dead giveaways. So I had to tighten all those screws and make sure my rhythms wouldn't be off kilter,” he said.

The 32-year-old sings Irish-American director Tarantino’s praises, saying he is “very clear” and “very thorough.”

“He gives you a lot of information to help you do your homework and then during filming you bring the flavors you've managed to discover in that process at home,” Fassbender said. “Then it's about the fun of discovering stuff and finding things out."

During filming for "Inglourious Basterds," which is an over-the-top film about Jewish Americans who go on a Nazi-killing spree, Fassbender said Tarantino would close his eyes "and concentrate on the rhythm" of the language during filming "like a piece of music.”

The result is a sweeping cinematic marvel. The actor said: "It's fantastical for sure but it fits perfectly with" Tarantino's over-the-top aesthetic and sensibility.