Jack Black Reacts to Being Cast as a 'Blowhard A**hole' in 'Don't Worry, He Won't Get Far on Foot' (Exclusive)

ET has an exclusive look behind the scenes at the making of Gus Van Sant and Joaquin Phoenix's new drama.

Jack Black's comedic star has only been on the rise lately, helping launch franchises with his hilarious turns in Goosebumps and Jumanji: Welcome to the Jungle, now here's something a little different: In Don't Worry, He Won't Get Far on Foot, he takes a darker turn as Dexter. "I think Dexter is kind of the devil," Black says in this exclusive look behind the scenes of the film.

Don't Worry, He Won't Get Far on Foot, from writer-director Gus Van Sant, follows Joaquin Phoenix's John Callahan, a hard-drinking, hard-partying cartoonist who lost his ability to walk after a car wreck. (The film is based off the real-life Callahan's memoir.) Dexter is, as Van Sant puts it, the "Mr. Partier Guy," a stranger who John meets on his last day walking and goes on a bender with, ultimately leading to the accident.

When Black was sent the project, he said yes immediately -- or, almost immediately.

"He's described as, like, a blowhard. I mean, that was a thing, when I first got the call, I was like, 'What?! Gus Van Sant? Joaquin Phoenix?!'" Black recalls. "And I read the script and I read the part and I was like, 'So, I wonder if Gus wrote the script and said, Who am I going to get to play the blowhard a**hole? Oh, I know! Jack Black!' I was really flattered and psyched, but a tiny part of me was like, 'Wait a second...'"

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Watch the trailer for Don't Worry, He Won't Get Far on Foot:

And here is the movie's official synopsis:

"John Callahan has a lust for life, a talent for off-color jokes, and a drinking problem. When an all-night bender ends in a catastrophic car accident, the last thing he intends to do is give up drinking. But when he reluctantly enters treatment -- with encouragement from his girlfriend (Rooney Mara) and a charismatic sponsor (Jonah Hill) -- Callahan discovers a gift for drawing edgy, irreverent newspaper cartoons that develop an international following and grant him a new lease on life. Based on a true story, this poignant, insightful and often funny drama about the healing power of art is adapted from Callahan’s autobiography and directed by two-time Oscar nominee Gus Van Sant. Jack Black, Carrie Brownstein, Beth Ditto and Kim Gordon also star."

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