<Li> Michael Gambon as Albus Dumbledore, the headmaster of Hogwarts and one of the greatest wizards of the age . Gambon assumed the role after Richard Harris, who played Dumbledore in the previous two films, died on 25 October 2002 . Despite his illness, Harris was determined to film his part, telling a visiting David Heyman not to recast the role . Four months after Harris's death, Cuarón chose Gambon as his replacement . Gambon was unconcerned with bettering or copying Harris, instead giving his own interpretation, putting on a slight Irish accent for the role, as well as completing his scenes in three weeks . Rumours of Ian McKellen being offered the role started to spread, but when asked he rejected the rumours and stated he had played a similar character in Gandalf of The Lord of the Rings trilogy . He also stated it would have been inappropriate to take Harris' role, as the late actor had called McKellen a "dreadful" actor . Harris's family had expressed an interest in seeing Harris's close friend Peter O'Toole being chosen as his replacement . </Li> <Li> Richard Griffiths as Vernon Dursley, Harry's Muggle uncle . </Li> <Li> Gary Oldman as Sirius Black, Harry's infamous godfather, who escapes from the Wizarding prison Azkaban after serving twelve years there for being falsely accused of being the Death Eater who betrayed Harry's parents to Voldemort . Oldman accepted the part because he needed the money, as he had not taken on any major work in several years after deciding to spend more time with his children . He drew inspiration from Cuarón, whom he described as having "such enthusiasm and a joy for life," and compared Sirius to John Lennon . He was "surprised by how difficult it was to pull off", comparing the role to Shakespearean dialogue . Oldman suggested Sirius's hairstyle, while Cuarón designed his tattoos . He had read the first book, and his children were fans of the series . The part made Oldman a hero with his children and their schoolmates . </Li> <Li> Alan Rickman as Severus Snape, the Potions teacher at Hogwarts and head of Slytherin . </Li>

Who played sirius black in prisoner of azkaban