17. Harry Accidentally Blows Up Aunt Marge - Prisoner Of Azkaban
In the first two films, Harry pretty much lives in terror of his aunt and uncle. And why not? They've always been cruel to him, and he was just a little kid. But in Prisoner of Azkaban, Harry is a 13-year-old with a pretty strong sense of self after being worshipped at Hogwarts for two years, and he's just not willing to put up with it. Aunt Marge says some really nasty things about his deceased parents? Well, she'd better get used to living life as a balloon, because Harry Potter isn't playing around anymore. It's amazing to watch him be so defiant to the people who had made his life miserable, and it's a far cry from the year before, when he was far more passive and deferential in his behavior with the Dursleys.