Genuine Reactions In The Great Hall
When they first stepped onto the Great Wall, they had a genuine reaction. Another fascinating aspect of the Great Hall was that when Harry, Ron, and Hermione walked into the set for the sorting hat scene, their reactions to seeing the hall were real! They had never seen the hall before filming the sequence, and it had a big impact on how they reacted.
It Was Apple Juice
The apple juice was used as a fake drink instead of the real butterbeer. The actors were actually drinking apple juice during the butterbeer scenes.