Dan has the hardest job because Harry on the page is the most difficult, the most nebulous. He’s just perfect, I think.

Rupert is just a genius. I don’t think anyone ever needed to tell him how to play Ron. He’s just known. Comedically he’s just spot on. You couldn’t teach that.

一 JK Rowling

Perhaps it had something to do with living in a dark cupboard, but Harry had always been small and skinny for his age. He looked even smaller and skinnier than he really was because all he had to wear were old clothes of Dudley’s, and Dudley was about four times bigger than he was. Harry had a thin face, knobbly knees, black hair, and bright green eyes. He wore round glasses held together with a lot of Scotch tape because of all the times Dudley had punched him on the nose. The only thing Harry liked about his own appearance was a very thin scar on his forehead that was shaped like a bolt of lightning.

“It’s called Time-Turner,” Hermione whispered, “and I got it Professor McGonagall on our first day back. I’ve been using it all year to get to all my lessons. Professor McGonagalll made me swear I wouldn’t tell anyone. She had to write all sorts of letters to the Ministry of Magic so that I could have one. She had to tell them that I was the model student, and that I’d never ever use it for anything except my studies… I’ve been turning it back so I can do hours over again that I’ve been doing several lessons at once, see?

"What’s that?" said Ron, pointing at a large dish of some sort of shellfish stew that stood beside a large steak-and-kidney pudding. 
"Bouillabaisse," said Hermione. 
"Bless you
,” said Ron.

"This was a profound moment because Ron had just left and it had affected both Harry and Hermione. There’s a line from the books where Hermione says, ‘You’re my best friend, Harry.’ And what’s sad is that she’s not Harry’s best friend - Ron is. There’s a loneliness there.”
 - Screenwriter Steve Kloves on Harry and Hermione’s dance scene.