Not sure if this really counts, but I'll tell my little story here...
I was at a late night party a few years ago, and most everybody was playing sardines with the lights out inside the house. I wasn't really interested in that, but I figured that I could play a little on thier piano. Since it was like 1 AM, I wanted something minor... and the first piece that came to mind was Rach's C sharp minor prelude. So I began, but I only played the first octaves mp so as no to really freak anybody out.

It was a lot of fun to play it without the lights on. Well, by the time I got to the agitato section, I was really getting into playing the piano in the dark with just the moonlight streaming through the window, when all of a sudden, I hear this scream... I mean a loud, terrified, blood-curdling, scream... from behind me, and then a soft thud.

It turns out that one of the girls was hiding in the shoe closet not that far behid the piano, and when I had stated to play, she was petrified, and thought a ghost was playing. She didn't want to look out, and by the time I got the the agitato, she just screamed, and passed out... I didn't have the heart to open the door and growl "MWHAHAHA..." At the same time, I did find it hysterical.

This could also go under "what's the funniest thing that came from your playing" but it can fit here to.

RnB