Uncle Vernon: And Dudley, you will be?
Dudley Dursley: I'll be waiting to open the door.
Uncle Vernon: Excellent. And you?
Harry: I'll be in my bedroom, making no noise and pretending that I don't exist.
In the dueling scene, when Snape pulls Malfoy back onto his feet, a cameraman is visible kneeling down on the far left of the screen.
The first scenes in the movie are some of the last scenes filmed. Viewers kind of tell by the way the actors' voices and looks changed. For example, Matthew Lewis (who played Neville Longbottom) said that he had to stuff cotton balls in his cheeks in the "Mandrakes in the Greenhouse" scene, since he had lost so much weight since the beginning of filming.