The smile on Dolores Umbridge’s face was fixed, and dangerous; the corner of her eye twitched when a rotting banana bounced off the shield above her, and Peeves soared away cackling to himself, "Necessary?" she whispered, her voice echoing across the hall, "Necessary?" she repeated, and Harry was beginning to grow concerned that a term and a half’s worth of torment had tipped her over the edge, "It is   necessary,  Professor McGonangall, because I   say it is necessary!!" her voice was suddenly a piercing shriek that had half of the school’s population drawing their breath in in alarm. Even McGonagall was shocked into silence.