Heath Ledger won the supporting-actor Academy Award on Sunday 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. The Australian actor's Oscar for the Warner Bros. blockbuster was accepted by Ledger's parents and sister. They accepted the Oscar on behalf of Ledger's 3-year-old daughter, Matilda.