A long time ago I used to pull lots of 24/36 hour shifts rather than ask for more devs. At about 3 am one night a bat flew past my head which freaked me out. I followed the bat, and then started to hear a loud pounding sound - I walked to the lobby to
see what it was, pretty freaked out, and it was coming from the pool table!
I walked over to the pool table, and it was coming from the floor below (construction work at 3 am!)