Harry Potter stars Matthew Lewis and Devon Murray popped in to support their friend Daniel Logan from Star Wars Episode 2, at an autograph signing.
Newsround Online's Genevieve Hassan caught up with them for a chat.
What are you all doing here?
Daniel Logan: I'm here signing at the Collectormania show.
Matthew Lewis: I was down at my brother's house and I thought Milton Keynes is on the way home, why not pop in and see these guys? Why, I dunno?!
Devon Murray: I was over in London getting ready to film on Tuesday so I thought I'd come over and hang with my two mates.
So how long have you all known each other?
DL: About a year and a half. We met at Collectormania last year.
What stuff have you three done together?
ML: All three of us have been doing signings together in America and at Collectormania.
Do you enjoy coming to signings and meeting the fans?
D: Yeah I do 'cos you get to meet up with your fans and talk to them and then meet up with people from different movies.
DL: I really enjoy meeting my fans 'cos I like to see how they view my acting and it makes me feel good and feel like it's worth doing it. Plus I love signing my name - when I'm at home I always just sign my name of blank pieces of paper! So it's fun.
ML: Well I always think that it's OK to make a film, but if you've got no fans there's no point 'cos without them there would be no film so it's good to come here and give something back.
DL: That's a good thought my friend... why couldn't I have come up with something as good as that?!
You're starting to film the Goblet of Fire on Tuesday...
D: Yes were are...
DL: And I'm going to visit them on set, so that should be fun.
D: And see Emma...
DL: (blushes) Errr...
And do you know what the first scene you're going to film is?
ML: No, I don't actually know.
Can you confirm whether John Malkovich is going to play Voldemort in the film?
D: Well that's what they were saying what everyone wants...
ML: Really!? That would be cool - I didn't know that. John Malkovich is really cool.
D: Originally that's what everyone wanted, but that's just a rumour going round.
There was also a rumour that Rowan Atkinson might be Voldemort?
ML: I heard that.
DL: Who Blackadder?!? They can't get Blackadder to play Voldemort!
ML: I heard a rumour that Rowan Atkinson was going to be in it, but no one knows to what character yet. But both those guys would be really cool.
You guys muck about a lot. Tell me funny story about what you've done together.
DL: We were in an Italian restaurant with James and Oliver Phelps (Weasley twins) and we thought: 'We gotta say it's the twins' birthday so the restaurant will give us free cake.' So me and Devon said to the waitress, 'hey, it's our friends' 18th birthday so can we get them some cake?'. Then they came out with cake and started singing Happy Birthday to them. And then everybody in the restaurant started too! The cakes actually cost us $6 for the prank, but it was still fun.