When I was little we used to play a game called "Dark room", we would hide in a room with the lights off, and someone had to find us. One day we were playing in my old room that had a black and white board on one side of the room. We all had as quietly as possible, because the person who would look for us could hear us hiding. After the game we turn on the light and the black and white board had moved places. We obviously suspected one of us at first but, we didn't hear anything and we all swore we didn't move it. Till this day we don't know how it happened...