LOS ANGELES (AP) – Heath Ledger won the supporting-actor Academy Award last night for his demented reinvention of Batman villain the Joker in "The Dark Knight", becoming only the second actor to win an Oscar posthumously.

Penelope Cruz claimed the evening's first prize, supporting actress, for her role as a tempestuous artist in Woody Allen's Spanish romance "Vicky Cristina Barcelona", while the robot romance "WALL-E" won for feature-length animation.

Ledger's triumph came exactly 13 months after his death from an accidental overdose of prescription drugs on Oscar nominations day last year.

His Oscar for the Warner Bros. blockbuster was accepted by Ledger's parents and sister. They accepted the Oscar on behalf of Ledger's three-year-old daughter, Matilda.

"I have to say this is ever so humbling, just being amongst such wonderful people in such a wonderful industry," said his father, Kim Ledger. "We'd like to thank the academy for recognising our son's amazing work, Warner Bros., and Christopher Nolan in particular for allowing Heath the creative license to develop and explore this crazy Joker character."

Since his death, the 28-year-old Ledger has gained a mythic aura akin to James Dean, another rising star who died well before his time.

The Joker was his final completed role, a casting choice that initially drew scorn from fans who thought Ledger would not be up to the task given Jack Nicholson's gleefully campy rendition of the character in 1989's "Batman".

In the months before Ledger's death, buzz on his wickedly chaotic performance swelled as marketing for the movie centered on the Joker and the perverted clown makeup he hid behind.

Ledger's death fanned a frenzy of anticipation for "The Dark Knight", which had a record $158.4 million opening weekend last summer.

The previous posthumous Oscar recipient was Peter Finch, who won best actor for 1976's "Network" two months after his death.

Best-picture front-runner "Slumdog Millionaire" scored in four early categories, claiming the adapted-screenplay prize for Simon Beaufoy, as well as the cinematography, film-editing and sound-mixing Oscar. The Harvey Milk film biography "Milk" won for original screenplay.

The epic love story "The Curious Case of Benjamin Button", which led with 13 nominations, had three wins, for visual effects, art direction and makeup.

"The Dark Knight" had a second win, for sound editing.

Cruz triumphed as a woman in a steamy three-way affair with her ex-husband and an American woman in Allen's romance.

"Has anybody ever fainted here? Because I might be the first one," Cruz said, who went on with warm thanks to Allen. "Thank you, Woody, for trusting me with this beautiful character. Thank you for having written all these years some of the greatest characters for women."

It's the fifth time an Allen film has earned a performer a supporting-acting honour. Cruz joins past Allen collaborators Dianne Wiest, a dual Oscar winner for "Hannah and Her Sisters" and "Bullets Over Broadway"; Michael Caine for "Hannah and Her Sisters"; and Mira Sorvino for "Mighty Aphrodite".

"Slumdog" writer Beaufoy, who adapted the script from Vikas Swarup's novel "Q&A", said there are places he never can imagine being.

"For me, it's the moon, the South Pole, the Miss World podium, and here," Beaufoy said.

"Milk" writer Dustin Lance Black offered an impassioned tribute to Milk, the pioneering gay-rights politician who was slain 30 years ago.

"If Harvey had not been taken from us 30 years ago, I think he would want me to say to all the gay and lesbian kids out there tonight who have been told they are less than by the churches, by the government, by their families, that you are beautiful, wonderful creatures of value, and that no matter what anyone tells you, God does love you and that very soon, I promise you, you will have equal rights, federally, across this great nation of ours," Black said. "Man on Wire", James Marsh's examination of tight-rope walker Philippe Petit's dazzling stroll between the towers of the World Trade Center in 1974, was chosen as best documentary.

The supporting-acting categories were presented by five past winners of the same awards. Cruz's award was delivered by last year's winner, Tilda Swinton, plus Eva Marie Saint, Anjelica Huston, Whoopi Goldberg and Goldie Hawn. Ledger's was presented by Kevin Kline, Alan Arkin, Joel Grey, Cuba Gooding, Jr. and Christopher Walken. It was a much different style for the Oscars as each past recipient offered personal tributes to one of the nominees, without clips of the nominated performances. Awards usually are done in chit-chat style between a couple of celebrity presenters. After last year's Oscars delivered their worst TV ratings ever, producers this time aimed to liven up the show with some surprises and new ways of presenting awards. Rather than hiring a comedian such as past hosts Jon Stewart or Chris Rock, the producers went with actor and song-and-dance man Hugh Jackman, who has been host of Broadway's Tony Awards.

Instead of the usual standup routine, Jackman did an engaging musical number to open the show, saluting nominated films with a clever tribute.