Why Didn't I Pay Attention To This Before?
From WB Official Harry Potter Website:
"In Harry Potter and the Prisoner of Azkaban, Gary Oldman plays Sirius Black, the eponymous prisoner whose escape is thought to pose a great threat to Harry Potter; Michael Gambon plays the role of Professor Dumbledore, Hogwarts' venerable headmaster; Timothy Spall portrays Peter Pettigrew, an old friend of Harry's father, James Potter, from their days at Hogwarts; David Thewlis plays Professor Lupin, the new Defense Against the Dark Arts Professor who harbors a mysterious secret; Pam Ferris plays Harry's overbearing Aunt Marge; and Paul Whitehouse portrays Sir Caddogan, a Knight who becomes the temporary guardian of Gryffindor Tower.

Reprising their roles from Harry Potter and the Chamber of Secrets are Daniel Radcliffe in the title role; Emma Watson as Hermione Granger; Rupert Grint as Ron Weasley; Robbie Coltrane as Hagrid; David Bradley as Argus Filch; Tom Felton as Draco Malfoy; Richard Griffiths as Uncle Vernon Dursley; Robert Hardy as Cornelius Fudge; Alan Rickman as Professor Snape; Fiona Shaw as Aunt Petunia Dursley; Dame Maggie Smith as Professor McGonagall; Julie Walters as Mrs. Weasley; and Mark Williams as Mr. Weasley.

Harry Potter and the Prisoner of Azkaban, a Warner Bros. Pictures and P of A production, will be distributed worldwide in 2004 by Warner Bros. Pictures, an AOL Time Warner Company"

And if wondering who is Gary Oldman, he's the guy who did Dracula in my all favourite Horror movie, Bram Stoker's Dracula. Boy! He's gonna fit the role nicely! -__^