Professor Trelawney is a character done rather badly by in the movies. Trotted out whenever the story demands a weird character or a bit foreshadowing, her biggest contribution, the prophecy fortelling Voldemort's destruction, is reduced to little more than a plot device propagating a generic chosen one plot. Still, Emma Thompson gives it her all, fully embracing the ridiculousness of the character and amping up the ambiguity of her real divination skills; she's memorable for her personality, if not her actions. Early on in pre-production Tilda Swinton was offered the part, but had to immediately turn it down due that recurrent issue, scheduling conflicts. Swinton subsequently said to the press that she'd never star in Harry Potter because she doesn't believe in it. No, she wasn't showing disbelief in magic; she's morally against boarding school.
