Robert Pattinson plays Cedric Diggory in Harry Potter and the Goblet of Fire.
Newsround chatted with him to find out how he got the part, what it was like playing cool Cedric.
Can you tell us a bit about how you got the part?
It's a pretty boring story. I did an audition, and then I was doing another movie. And I did the other movie and I came back. The day I came back I had a call back.
I went in, met Mike Newell. Actually, I met Mike Newell twice and the second (time) he said: "You got the part". So it's quite short and sweet!
How did you feel when you realised you got it?
I don't know. Like, I basically just started acting. I did two other movies and a few plays before but I kinda done them one after the other, so I didn't really know what I was doing then. I still don't really now. So I was kinda like: "Oh, okay!"
Had you read any of the Harry Potter books before?
No. I just read it (book four) before the audition. I've read three and five now as well, and I'm halfway through six!
What were your first impressions of Cedric?
I think he's a pretty cool character. He's not really a complete cliché of the good kid in school. He's just quiet. He is actually just a genuinely good person, but he doesn't make a big deal about it or anything.
He's just like, whatever. I can kind of relate to that. He's not an unattractive character at all and his storyline is a nice storyline to play.
Cedric is a bit of a heart-throb - how do you feel about playing him?
That is quite difficult. In the book and also my first introduction of the script is like "an absurdly handsome 17-year-old" and it kind of puts you off a little bit, when you're trying to act, and you're trying to get good angles to look good looking and stuff.
It's really stupid; you'd think I'm really egotistical. But I think that's the most daunting part about it - it's much scarier than meeting Voldemort!
Of course, he's Harry Potter's love rival, because you meet Cho Chang first - so did you joke around on set that you're not supposed to like each other?
I don't know. I think he's (Daniel) , just in real life, he's just so far superior to me in terms of desirability, so he didn't really have much of a competition with me. So there wasn't really much joking around. I'd probably cry if he did.
If I was Katie, I would definitely go out with him because he's rich and famous, and I'm not really.
Did you get on well with the rest of the cast? Like Cho for example?
Yeah. I get on really well with Katie, she's a really cool girl. I don't have many talking scenes (with her).
Most of my scenes, like big scenes, are just with Dan. I dance with her, and there's a lot of scenes like holding hands and stuff like that. But I get on really well with her. She's a nice girl.
Are you ready for Pottermania?
I have no idea. I've been using the fan websites as I was acting it, because they know so much about the books, and it's really helpful as a resource.
But, I don't know. I have no idea. Someone asked for my autograph the other day which is quite cool. But, I don't know. I hope it doesn't make me not come out of my house, because I barely come out of my house as it is! So, we'll see.
But you know you're gonna be a heart-throb!
I don't know. Maybe. I don't know. I'm quite immature so that's quite good, so I prefer to be a heart-throb!.
There's a lot of action scenes - what was the best bit for you?
I liked the maze part. The maze was really fun. A lot of the stunts are very contrived, and someone's practised them a hundred times and you have to get it perfect otherwise it's pointless doing it.
You're not gonna be in the right shot or anything. But in the maze, a lot of it was on steady cam - which is just a guy running around with a camera - and all the hedges moved.
So me and Dan were basically chasing each other around and punching each other, with these hedges squeezing us.
And the camera would just follow you around, so you could basically do whatever you wanted. It was really fun. There were lots of cuts and bruises afterwards and it felt like you were doing a proper job!
And did you learn to scuba dive for the diving scenes?
Yeah. I had a lot of diving. I think I was doing the underwater stuff for about two months. And, so I think I did about three weeks of learning how to scuba dive.
You learn how to do it in a little bathtub-sized thing with all the stuff on, and then on the first day of shooting in the tank, you have to hold your breath and there's nothing there!
And the tank is 60 feet deep and you're holding your breath for about a minute and a half. Probably not actually! Maybe about 30 seconds.
Was that one of the hardest things you have to do?
Yeah, you get used to it though. I really liked it after a while. I though it was really calming. You'd really concentrate on what you're supposed to be doing.
You can't talk to anyone so you stay completely in character. You can't see anything so all you can hear is your director through the water, saying like "look scared". It was pretty fun. It was really fun!
Were there any bad parts about being on the Harry Potter film set?
No, not really. Not at all. It was a really long shoot so it was kinda tiring by the end, but I was on it for about 11 months or something. But all in all it was really fun, and there were a lot of amazing periods, which was really nice.
Did you find yourself star struck by the big name adult stars?
Yeah, I did. I'm a big fan of Michael Gambon. They were all really, really nice people and they treat it as a job. They don't really have big egos or anything about it. There was one guy - Warwick Davis - he's in [the film] Willow, and Willow is like my favourite film.
I had one scene sitting next to him at the dragon task, and I had no idea what to say to him at all! He was the only person I asked for an autograph the whole way through it!
What are your feelings about the premiere?
I don't know. I've been to a couple of Warner Bros films in the last few weeks, and considering no one knows who I am, it's still a pretty scary event.
So I don't know what it's gonna be like when you actually have to do something rather than just walk in. I still trip over my feet and stuff when I'm not supposed to be doing anything. So, I'll just see how it goes. I'm looking forward to it.