My favorite character are Hagrid and George. Hagrid speaks funnily for example he would say : "I woo like ter gi yer a giff." Instead of saying : "I would like to give you a gift."
I also like George Weasly even though he is not there in the story much. I like him because he is really funny, he knows all the secret routes out of the school and inside the forbidden forest. He is also the schools biggest prankster.
Actually the whole Weasly family is funny.
My advice is to read the book before watching the movie to understand and enjoy the movie better.