Emma Thompson's fanbase is about to get a lot younger. The English actress has signed on to play Professor Trelawney in ''Harry Potter and the Prisoner of Azkaban,'' according to Variety. Trelawney is Hogwart's School of Witchcraft and Wizardry's dotty divination teacher, known for her ever-inaccurate predictions (she constantly says that Harry's death is imminent). The character reappears in the other Potter books, and will presumably do the same in the movies.
''Prisoner of Azkaban,'' which includes now-teenage returning stars Daniel Radcliffe, Emma Watson, and Rupert Grint, hits theaters next July. Among the other newcomers to the ''Potter'' franchise is Gary Oldman, who plays the mysterious Sirius Black. Luckily, Thompson's ex-hubby, Kenneth Branagh, isn't likely to reprise his role as the vain Professor Gilderoy Lockhart -- at least not in ''Prisoner.''