In the Subway: the train stops in the tunnel, lights go out. Then the announcement: dear passengers, we are not the hogwarts express and we are not going to be attacked by Dementors. It was just the wrong button.
Hahaha, it's funny 'cause it's true. The house points were just disproportionate in general. "Harry, you snuck out after curfew, minus 800 points from Gryffindor. However, you saved us all from Lord points to Gryffindor!