Harry's best friend admits he's a huge JK Rowling fan. 13-year-old Rupert revealed in his interview with Newsround's Lizo Mzimba that he got the dream part after reading about the auditions right here on this website.
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How did you get involved with the film?
I found out that you could audition by sending a picture of yourself and some information to Newsround. I did my own video with me, first of all, pretending to be my drama teacher who unfortunately was a girl and then I did a rap of how I wanted to be Ron and then I made my own script thing up and sent it off.
What was it like seeing the set for the first time?
Walking into the great hall for the first time was absolutely incredible - all these effects with all the candles floating in the air, all lit and everything, food on the table, all the flambeaus were lit - it was just incredible, it was the most amazing thing I've ever seen in my life.
Tell us about filming the scene with huge chess figures close to the end of the movie
I think the chess thing was pretty difficult because there was loads of dust everywhere and the pieces were really big - I got to sit on a horse which was really fun.
It was Ron's turn in the limelight because all the way through the film Harry's been the one who's been doing all the brave stuff and Ron felt a bit bad but he felt happy for Harry because he's his best friend. But I think Ron was really happy because that's his thing - chess really.
What was it like doing stunts?
Well one of the times I did a stunt was in the devil's snare room and they lifted me up on a harness and a safety rope really, really high, and they just dropped me down into the devil's snare. That was really fun, my heart stopped halfway through because then I was afraid of heights but now I'm not so afraid of them.
There are some people who aren't too keen on a movie that they believe may spoil the imagination of the books forever.
I am a really big Harry Potter fan and I've seen all the sets, I've lived Harry Potter and I don't think it's destroyed the books at all, I think it's really spot on.
It's been an incredible year for Rupert - magically plucked from obscurity to become a film star.
It's going to be really weird to know that people are going to actually know my name, that's going to be strange.
Are you looking forward to being famous?