Katie Leung plays Cho Chang in Harry Potter and the Goblet of Fire.
Newsround chatted with her to find out how she got the part, what it was like filming and most importantly, what Daniel Radliffe is like!
Tell us how you got the part of Cho?
My dad saw an advert on telly for the character - you had to be 16, of oriental appearance and live in Britain so it fitted me perfectly.
I went down to London, queued for hours and hours and then they took a photo of me and said they'd call me in two weeks if I fitted the role. I went through a series of auditions and I did a screen test which was great fun.
You hadn't done acting before?
It had never been of interest to me because I thought if you wanted to be an actor you had to be confident in front of so many people and I'd always been really shy at school.
How did you feel when you got the part?
I was sleeping when my mum rang and told me so I had to call her back when I woke up just in case I was dreaming!
How has life changed for you?
Not much apart from meeting new people and making lots of friends. I'm now thinking about going to university and my career.
I have no set plans at the moment. I would like to go to university - even if I hadn't got the part, but this is a once in a lifetime opportunity so I'm not going to miss that.
Were you a Potter fan before you got the part?
I was a great fan of the films and had read the first three books, but didn't read book four and five until after I got the part. Those are the books that Cho's mainly in so I didn't really get to know her character until then.
What's Daniel Radcliffe like?
He's great - he's so down to earth. You don't expect it because he's so famous and known worldwide but he's just like the rest of us and we're really good friends.
Was it daunting to meet him?
When I first met Dan we did a drama workshop which was nerve-wracking as I had to act in front of him, but he made it so easy for me and he's so friendly.
Do you think Cho and Harry make a good couple?
Not particularly as Harry's got enough problems in his life and she has a boyfriend.
What do you think about the prospect of snogging in film five?
I'm really excited about it! I think it'll be quite funny with everyone watching, but I'll need to wait and see.
Have you seen the film yet?
I've seen the trailer - it's amazing how they can put it all together and make it look so good.
Are you prepared for Pottermania?
I'd say I'm prepared but I don't know what it'll be like - I'll have to wait and see.
Have you been given any tips?
I've been told to stay grounded and not let it go to your head, but to make the most of it.
What was the best part of filming?
Being able to meet so many incredible people. I learnt so much from doing this film and we've kept in touch.
And what was the worst bit?
The long hours and doing the same scene over and over again. But it's worth it in the end because you get better every scene.
Were there any difficult bits? You had to learn some new skills for the film.
We did a lot of diving scenes and I had a lot of lessons but it was a great experience. A lot of co-ordination was involved - using the wind and wave and you had to swim to a certain angle.
Were you star-struck at any of the famous actors you worked with?
All of them! There wasn't anyone in particular as I didn't have many scenes with them but they were usually in the Great Hall when we were all together. But it was daunting for everyone to see them.