Funny, I don't recall the point when I stopped being a prat.

And you know, most of the time it really isn't about what you say with these people, it's how you say it. If I saw you and they were saying Sally Anne in the common room, for example, I'd say, "What do we have here? Why, if it isn't the cleverest little half blood at school," and they'd all think I was taking the mick on Sally Anne, but the joke's on them, see, because I'd actually be speaking the truth, and Sally Anne would know it.

Or - remember when I told Umbridge I'd caught Fawcett in the Forest, but she'd punched me like an animal and was dragged away by centaurs, and that I hoped they'd eat her?

That's what allowed the rest of you to help her escape.