She also said one character was constantly on the receiving end of her sharp tongue: "Hermione always has some snooty lines for Ron. He gets the worst of it really."
'Stunts were fun'
Emma also told Newsround's Lizo Mzimba that she really enjoyed all the stunts the actors had to perform for the film:
"In the troll scene there were lots of stunts. That's one of the reasons I enjoyed it, but it was hard as well.
"I had to do lots of darting under sinks, running through legs. But they haven't used all the stunts I did and that's just not good enough!"
Top secret filming is just getting underway for the second Harry Potter adventure - The Chamber of Secrets.
Emma says: "The thing I'm looking forward to most is how they're going to make me look like a cat. That'll be very interesting."
The movie has its world premiere on Sunday and opens across the UK on 16 November.
And don't forget - on Wednesday we'll have the exclusive interview with Harry himself - actor Dan Radcliffe.
So don't you dare miss it!