What sort of background do you need to be an actor? These days, it’s not exactly required that you graduate from the Actors Studio (or from anywhere else), but when I look up the credits of even the lamest supporting actors in bad Hollywood comedies, they tend to come with a long string of professional experience (“After a four-year run on the popular Nickelodeon series, Allegra made her big-screen debut in She’s All That and went on to co-star in…”). As for indie-film actors, they often bounce back and forth between no-paycheck Sundance movies and big-paycheck schlock. So I was surprised when I got back to my room after seeing Douchebag, a bubblingly sharp and fresh and dark and winning comedy about a major, major a—hole, and learned that the movie’s mesmerizing lead actor, Andrew Dickler, started out as a film editor (he was an apprentice on Pulp Fiction) and since then has been…a film editor. Period. He has never acted before.

The thing is, he looks like a film editor, which grounds the movie, from its first funny moments, in a kicky, downbeat reality. The title dickwad, Sam Nussbaum, is about to get hitched to the very sweet and beautiful Steph (Marguerite Moreau). They live in Los Angeles, but Sam still favors the style of Seattle: He wears oversize grunge shirts, and he’s got one of those bushy postmodern hippie beards I think of as early-Spin-Doctors-meets-Zack-Galifianakis. Behind that fuzzy facial armor, he speaks his mind, coldly and cuttingly, especially when he’s talking to his younger brother, Thomas (Ben York Jones), a shy, polite loser-slacker who’s trying to become a painter while still sponging off mom and dad.

Tom has to be dragged down to L.A. five days before the wedding, and once he’s there, it’s clear that the two brothers hate each other (we’re not certain why). Sam rags, mercilessly and hilariously, on Tom’s artistic efforts (“Do you still do those doodles?”), and the moment that Dickler, who has sensitive/beady eyes and the crack timing of a Vegas insult comedian, started to spew that testy aggression, I was grateful — so grateful — that I wasn’t stuck at another hip yet weak-tea cautious and “liberal” mumblecore romance. Sam is more like the Larry David of the texting generation.

Douchebag, thank God, isn’t ersatz-mumblecore, like last year’s middling twentysomething Sundance attention-getter, Humpday. As directed by the gifted Drake Doremus, whose first film was last year’s Spooner, this is more like talky-core. When Sam learns that Tom is still smitten with the girl he had a crush on in fifth grade, he forces his brother to go along on a buddy road trip and find her (he’s got other motivations as well), and the movie turns into a rambly minimalist Sideways. It’s fascinating to discover that Sam, with his balding, tall-geek look and noodgy ability to annoy, is a major chick magnet. Douchebag is a movie that understands, from the inside out, why even nice girls like jerks. The movie, though, is finally about two brothers who have pushed each other apart for so long that they don’t even know the damage their broken bond has caused them. In its way, Douchebag is a touching love story. It’s just not the love story you expect.

More from Owen Gleiberman at Sundance 2010:

Blue Valentine: Ryan Gosling and Michelle Williams shine in soulful, wrenching marital drama

The Runaways: Kristen Stewart and Dakota Fanning rock out

Sundance 2010 documentaries: Casino Jack and the United States of Money; Smash His Camera; Restrepo

The Company Men: A juicy drama of downsized corporate executives

Howl and Nowhere Boy: The fascinating early days of Allen Ginsberg and John Lennon

Sundance 2010: Change you can believe in?

More from EW at Sundance 2010:

Ryan Reynolds’ Buried sold to Lionsgate