4. Richard Harris/Michael Gambon - Albus Dumbledore
Depending on how you like your old men, here's a movie recasting that has continued to polarise opinion, though there's not much to say about it, really, consider that the original actor is dead now, and a replacement was therefore essential. In the first Harry Potter movie, of course, wonderful movie icon Richard Harris was cast as jolly Hogwarts headmaster Albus Dumbledore. Some said he was too frail for Dumbledore, but Dumbledore is sort of frail, from what I remember, so it always made sense to me. Unfortunately Harris passed away before the third movie,
Prisoner of Azkaban, started filming, so it was Michael Gambon - like Brian Cox, another actor of raving sensibilities - who stepped in to fill his wizard-sized boots. And though Harris will always remain the definitive on-screen Dumbledore in my own mind, Gambon perhaps better embodied the later-stage "action" Dumbledore of Rowling's novels. One can hardly imagine Harris leaping around the screen quite as easily as Gambon managed, though they probably could have CGI'd his limbs or something. That's what they do now, isn't it?