They're the biggest bullies at Hogwart's.
And the boys who've been chosen to play Draco Malfoy and his sidekicks, Crabbe and Goyle, spoke to Blue Peter about what it's like to star in the first Harry Potter film.
Watch the interview by clicking on the video link on the top right of this page.
Jamie Waylett who plays Crabbe, told how he got the part.
He said: "Someone told me they were going to make a film of Harry Potter and I thought it's going to be cool. I didn't even know it hadn't been made yet! Then a casting agency came to our school and picked four of us and spoke to us and took Polaroid's. Then they told my headmistress they wanted me and it just kicked off from there."
Joshua Herdman, who plays Goyle, said the worst thing about his character was being a bully and looking mean.
Tom Felton who plays Draco Malfoy, spent four months filming the first movie and assured Harry Potter fans he would be back for the second.
The boys also described their favourite scene from the film. Jamie and Joshua agreed the best bit was the Hallowe'en scene.
Jamie said: "The tables came up to my knee height and we all have to run out when everyone starts screaming but I kept falling over my robe and everyone kept falling on top of me. It hurt!"
But Tom said it was the Quidditch scenes where he and his classmates learn to fly.