Ah, the old 'scare prank', the beloved format where unsuspecting people are placed in a scary situation, and then someone is sent along to give them a fright.
The crew from movie The Conjuring 2 decided to go with this for a promotional event in Australia, inviting an audience to an exclusive viewing in a warehouse, asking them to stick around for a post-screening interview, and then setting up a two-way mirror with a scary nun on the other side to make them screen. Obviously. And it worked, there are some pretty satisfying reactions, the ones you would expect when scaring people with an undead nun coming at them.
But the thing that truly makes the thing worth watching happens right at the end when the last subject gets a small fright from the nun in the mirror, and then turns and sees another nun in the room with him.
What happens next is extremely funny, and very satisfying.