reverse-psycho

When a person in the shower creepily peeks out from behind the curtain to startle another person who is also using the bathroom. So named because it's a role-reversal of the famous scene in the movie Psycho.

Jane came in to a dump while I was in the shower. She nearly shat out her colon when she noticed me staring sideways at her beside the shower curtain like a tipped-over garden gnome. Pulled the reverse-psycho on her.