Gus Van Sant’s Don’t Worry, He Won’t Get Far On Foot took its Sundance bow at the Eccles last night, introducing the Park City crowd to the tragic story behind Portland, OR cartoonist John Callahan. An alcoholic since his childhood years, Callahan was crippled in a drunken automobile accent, and soon after discovered a passion for cartooning that kept him going as he fought his alcoholism.

Van Sant was familiar with his fellow Portland native. “He was often on the streets beating very fast up and down,” he told me at Deadline’s Sundance Studio. “He was kind of a thrill seeker in his souped-up electric wheelchair.”

In fact, Van Sant met Callahan, who died in 2010, after Robin Williams, who had starred in van Sant’s Good Will Hunting, first approached him with the option to star in a biopic about the cartoonist. “Robin had followed his cartoons,” Van Sant said. Williams, too, was great friends with Christopher Reeve, who had been similarly disabled in a riding accident. “I think it was in honor of Christopher, partly,” that Williams wanted to do the film, “and also [it was] about a very funny person.”

Both men have since passed, and Joaquin Phoenix plays Callahan in the final film, alongside Jonah Hill as the charismatic AA sponsor who helped the cartoonist find a reason to live, and Jack Black as the drinking buddy whose impaired driving caused the accident that would change Callahan’s life.

Van Sant was joined in the studio by regular collaborator Danny Elfman, who scores the film. “Because it was Gus, I just kept everything loose,” he said. “I’ll write him stuff and play it for him and he’ll go, “What other kinds of weird stuff do you have lying around?”

Check out more in the video above.

The Deadline Studio at Sundance 2018 is presented by Hyundai. Special thanks to Calii Love.