hogwarts filmset

so you know how there are actors like tom felton and Daniel raclif played the harry potter characters in the movies right? so um lets say they are and the filming crew are inside the hogwarts and suddenly they meet the actual characters after filming the first scene of prisoner of Azkaban. first one to see them is draco malfoy and pansy Parkinson. and the student actors are all teenagers and the professors are all there , so yeah crazy right . you can other be a background character, fan or an actual book character or one of the actors or filming crew