457970771RT138_Celebrity_Si Photo: Sundance

The 30th annual Sundance Film Festival began with a literal drumroll in the form of the ferocious opening-night movie, Whiplash, which pits a jazz-drumming prodigy against his teacher in a battle of wills. It quickly sold to Sony Pictures Classics for a reported $3 million, propelled by lead performances by Miles Teller, pounding the skins until his hands bleed, and J. K. Simmons, abandoning his usual dopey-dad mode to play a drill sergeant of a band conductor. The theme of the movie — the pursuit of one’s passion beyond all reason — seemed to set the tone for the rest of the festival, with many other actors following Simmons into unfamiliar territory. Here are a few of the performances we’ll be beating our drums for this year.

*This article is an expanded version of one that appears in the February 3, 2014 issue of New York Magazine.

In his first lead movie role, the Saturday Night Live alum plays Milo, a gay failed actor who moves in with his twin sister (Kristen Wiig) after he attempts suicide — but there’s a warmth that slowly bubbles up from Milo’s misery. Hader shot the suicide scene a year ago, the same day he played Kate Middleton’s gynecologist in an SNL sketch. “I was like, What world am I in right now?” he says.

Plenty of screen comedy has been mined from man-boys who refuse to grow up, but at Sundance, a counter-revolution is brewing: Women now get to plumb their Peter Pan syndromes, too. No one did it better this year than Knightley in Lynn Shelton’s Laggies, where she plays a layabout who ducks her boring fiancé’s marriage proposal and decides to regress and misbehave with a new teenage friend (Chloe Moretz) instead.

Director Richard Linklater shot Boyhood in tiny increments over the past twelve years, so we see Coltrane age from 7 to 18 before our very eyes. “Later on, the character started to merge with my actual life, and it became much easier,” says Coltrane, who filmed his final scenes last October: “I was feeling this great relief and sadness at the same time.”

As the front man of a very unusual rock band, Fassbender spends the entirety of the film wearing a giant papier-mâché mask, hiding all those jagged, striking planes of his increasingly famous face behind the wide eyes of a demented-looking cartoon character. Strangely, it works — Fassbender is comically charming using just his voice and gangly physicality. “He was very comfortable in the head,” says director Lenny Abrahamson.

Bill Hader isn’t the only former SNLer to impress at Sundance this year: Jenny Slate notched a winning, breakout performance in the unlikely “abortion rom-com” Obvious Child. As a stand-up comedian who becomes pregnant from a one-night stand, then must wrestle with whether to tell the father as she begins to date him more seriously, Slate is a crack-up — obviously — but her croaky voice hides real reservoirs of hurt, and she’ll make you cry when you’re least expecting it.

Best known for a supporting role on Veronica Mars, Thompson breaks out as a biracial college student, Sam, who hosts an incendiary radio show issuing edicts like “Dear white people, stop dancing.” Thompson exposes extra dimensions of her college-radical character as she struggles with her own racial identity and overcompensates to fit in with her black peers.

As a vicious college music teacher who pushes a young drummer (Miles Teller) to his physical and mental limit, Simmons gives the most intense performance of his career. Director Damien Chazelle joked that he told the actor to go beyond even his work as the loathsome neo-Nazi villain on HBO’s Oz, saying, “I want you to make him look like the teacher in Mr. Holland’s Opus.” Photo: 2013

The premise sounds like a joke: An isolated Japanese woman finds a VHS tape of Fargo in a cave and ventures to Minnesota in search of the money Steve Buscemi’s character buried at the end of the film. Kikuchi portrays Kumiko not as a lunatic but as a dreamer determined to escape her enervating job and overbearing mother, even if the only words she can speak in English are “I want to go Fa-go.”

No one but Mark Ruffalo could play the central character of Infinitely Polar Bear — a bipolar dad who loves his two daughters as much as he frequently endangers them — and have you actually root for him this much. You need Ruffalo’s warmth and charisma to counterbalance his forays into irresponsible insanity, and the tough balancing act he pulls off may be his best performance yet.

Bodily fluids and vegetable-oriented sexual fetishes get top billing in this German-language comedy about a young woman dealing with her parents’ divorce, Sundance 2014’s most vulgar entry . But the charming Juri shines through anyway, somehow making her character’s predilections — like masturbating with an avocado seed while in the hospital for rectal surgery — oddly endearing.

First-time actor Wiggins, discovered off of YouTube videos he’d made with his friends, has the heavy task of carrying this South Texas drama about an all-male family falling apart, told through the eyes of his character, 13-year-old delinquent and aspiring motocross racer Jacob. But he never strikes a wrong note, whether he’s being an overprotective big brother, butting heads with his neglectful, alcoholic father (Aaron Paul), or just being a scared, angry kid who’s lost his mom, with all the raw, inexpressible emotions that entails.

Only the first half of Lars Von Trier’s ultra-NC-17 magnum opus screened at Sundance, but Thurman steals it in what we’ve seen. As Mrs. H, she enacts every spurned wife’s fantasy by showing up with her three small boys to the apartment of the young, titular sex fiend (newcomer Stacy Martin) for whom her husband’s just left her. And, instead of exploding in anger, she sticks around past the point of discomfort out of deep concern for making sure daddy’s settled into his new home — even having dinner with her husband, his mistress, and her next lover, who’s shown up right on schedule. A guilt trip for the ages.

This is the role the Parks and Recreation star was born to play. After dying from a snakebite, Plaza’s Beth mysteriously returns to continue dating her boyfriend (Dane Dehaan) without realizing anything has changed. Plaza nails Beth’s transformation from really horny, slightly off Beth 2.0 to car-eating, home-destroying, smooth-jazz-loving zombie. “I weirdly enough have this demon voice that I’ve been doing since I was a kid,” says Plaza. “I guess I’ve been preparing my whole life for this part as a zombie. I just hope my mommy’s proud.”