What non-actor was cast in an acting role and did an amazing job?
Jason Lee in Mallrats.
Lee was a professional skateboarder, not an actor, but in 1995, at 25, he wanted to retire from skating and try something new. Casting director Don Phillips brought him in to audition for Kevin Smith, and Lee won the role of slacker manchild Brodie Bruce in Smith's sophomore effort.
In the film, Brodie was the best friend of T.S. Quint, who was played by established actor Jeremy London, but Lee acted circles around London, and pretty much stole the whole movie. Brodie is obnoxious as fuck, but Lee is so charming and funny that the audience loves him anyway. (This is reflected in the film, where Brodie is ultimately offered his own late-night talk show.)
His performance in Mallrats kicked off a very successful acting career. To date, he has over 70 credits on his filmography, including memorable roles in the films Chasing Amy, Dogma, Almost Famous, Enemy of the State, and Vanilla Sky, and his Golden Globe and SAG Award nominated role as the title character in the sitcom My Name is Earl.
Kevin Smith told the story of Lee's casting in a 2020 interview with Entertainment Weekly:
Our casting director was the great Don Phillips. Don was famous in town for casting Fast Times at Ridgemont High. He had discovered Sean Penn. For us, he discovered Jason Lee. Jason Lee was a professional skateboarder who had never really acted before. So, Don Phillips goes, "I got a kid coming in today, and he’s never acted before, and he’s a professional skateboarder." I didn’t know much about the skate game. He comes in and he's green as hell. He's never really acted. We’re making chit-chat and I was like, "So I understand you’re a skateboarder." And he’s like, "Well, I just retired." And he looked like he was f---ing 23. So, I’m like, "You retired?" He goes, "I’ve been skating at a professional level for ten years, yeah. I want to put it aside now and I want to concentrate on a different discipline."
He was so well-organized. I loved his delivery. It was so not-polished and so real and rough and funny. All the guys came in to read for TS (the role ultimately played by Jeremy London), all the girls that came in read for Brandi (who would be played by Claire Forlani). So, when Jason was done with his audition, Don Phillips was like, "Do you want him to come back?" And me and Scott Mosier (Smith's regular producer) were like, "Well, he's a really good guy, I don’t think he’s right for the part, but bring him back, because he’s fun to talk to." We kept bringing him back because we didn’t know anybody in Los Angeles and we just thought he was a nice guy. Eventually, he wound up being better than everybody else. I said, "Listen, I think we’ve figured it out, we want you to play Brodie." And I’ll never forget, he was eating, and he looks up for a brief second, and he goes, "Yeah?" and he goes right back to eating his sandwich, looking back down. Eating was more exciting than being cast in his very first movie at that moment in time. But he came out and absolutely crushed, man, and he was a delight.