"Crash" crashed the party.

Leading nominee "Brokeback Mountain" was widely expected to win the best picture Oscar at Sunday night's 78th annual Academy Awards, but "Crash," an ensemble drama about racism in Los Angeles, took the prize.

"We are humbled by the other nominees in this category. You have made this year one of the most breathtaking and stunning maverick years in American cinema," said "Crash" producer Cathy Schulman.

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"Crash," which also won for best original screenplay, scored a similar upset at the Screen Actors Guild awards in January, winning best ensemble cast. Nevertheless, it was one of the biggest upsets in Academy Awards history.

But gay cowboy movie "Brokeback Mountain," which was up for a leading eight awards, didn't go home empty-handed. Ang Lee won for best director, becoming the first Asian filmmaker to receive that award.

"I wish I knew how to quit you," Lee quipped, referring to the film's oft-quoted line.

"Brokeback Mountain" also picked up the Oscar for adapted screenplay by Larry McMurtry ("Lonesome Dove") and Diana Ossana as well as for Gustavo Santaolalla's musical score.

Reese Witherspoon won best actress for her role as June Carter Cash in "Walk the Line," thanking the movie's creators for "helping me realize my lifelong dream of being a country music singer."

She also thanked co-star Joaquin Phoenix and her grandmother for teaching her about "strong women."

Witherspoon was favored to win the award, but had a tough rival in "Transamerica" lead Felicity Huffman.

Philip Seymour Hoffman won best actor for his work in "Capote," a performance that even people who knew Truman Capote said was right on the money.

"I'm overwhelmed, I'm really overwhelmed," Hoffman said, thanking his mom for raising four kids alone and taking him to his first play.

Hoffman was considered a virtual shoo-in for the prize.

George Clooney won for supporting actor for the oil-industry thriller "Syriana," and Rachel Weisz took the supporting actress prize for another corporate thriller, "The Constant Gardener."

"All right, so I'm not winning director," Clooney joked after winning the first award of the night.

Clooney, who effaced his glamour-boy looks behind the bearded, heavyset facade of a CIA patriot who grows jaded over U.S. policy in the Middle East, was the first actor in Oscar history to be nominated simultaneously for acting in one movie ("Syriana") and directing another ("Good Night, and Good Luck").

Weisz, who won for her role as a humanitarian aid worker who takes on pharmaceutical practices in "The Constant Gardener," thanked co-star Ralph Fiennes and director Fernando Meirelles, "and of course, John le Carre, who wrote this unflinching, angry story."

Among the other awards, the raucous hip-hop tune "It's Hard Out Here for a Pimp" from "Hustle & Flow," whose expletive-laden lyrics had to be toned down for performance on live TV, won the prize for best song. The song was written by the rap group Three 6 Mafia — aka Jordan Houston, Cedric Coleman and Paul Beauregard.

Featuring dancers dressed as hookers and pimps gyrating on stage, the song's performance stood in sharp contrast to the other nominated tunes and the general stateliness of the Oscars.

"You know what? I think it just got a little easier out here for a pimp," joked first-time Oscar host Jon Stewart.

The stop-motion family tale "Wallace & Gromit: The Curse of the Were-Rabbit" won the Oscar for best animated feature film.

The Antarctic nature tale "March of the Penguins," a surprise smash at the box office, was honored as best documentary.

"King Kong," from "Lord of the Rings" creator Peter Jackson, won three Oscars, for visual effects, sound mixing and sound editing. The Japan drama "Memoirs of a Geisha" also earned three, for cinematography, costume design and art direction, while the fantasy epic "The Chronicles of Narnia: The Lion, the Witch and the Wardrobe" picked the prize for best makeup.

South Africa's drama "Tsotsi" — based on Athol Fugard's novel about a young hoodlum reclaiming his own humanity — won for foreign-language film, beating the controversial Palestinian terrorism saga "Paradise Now."

Clooney was one of the marquee names among a lineup of acting nominees heavy on lesser-known performers. And with a best picture field of lower-budgeted films that drew smaller audiences than the commercial flicks that often dominate the Oscars, the question was whether Hollywood's big awards night could lure TV viewers.

Oscar organizers hoped Stewart and the cultural buzz over front-runner "Brokeback Mountain" would beef up viewership.

The Oscars generally lure their biggest audiences in years when blockbusters such as "Titanic" or "The Lord of the Rings: The Return of the King" are favored to win.

"Brokeback Mountain," though, has become a phenomenon far beyond those who have actually seen it, entering the pop culture psyche with its tale of cowboys in love — scoring acting nominations for both Heath Ledger and Jake Gyllenhaal.

The show began with reprise visits from former Oscar hosts Billy Crystal, Chris Rock, Whoopi Goldberg, Steve Martin and David Letterman, in which they all turn down offers to do the show again.

Crystal and Rock did a "Brokeback Mountain" spoof, the two sharing a mountainside tent like the cowboys in the film and begging off as hosts, saying they were too busy.

ABC, which aired the show, and the Academy of Motion Picture Arts and Sciences assembled an A-list collection of Oscar presenters to help offset a relatively unknown cast of nominees.

Oscar nominees in most categories, such as directors, actors and writers, are chosen by specific branches of the Academy of Motion Picture Arts and Sciences. The full academy membership of about 5,800 is eligible to vote in all categories themselves.

The Associated Press contributed to this report.