They're watching some really good porn :S Though I don't actually know, I'm just in the room next door :/
One time, we had a couple staying over so my parents volunteered my room since I have a double bed. So I was forced to sleep downstairs in the living room which is directly below my room. Yes, you see where this is going. I wake up one day to this constant squeaking and thumping. Yup. And it went on for a good while. So little sleep for me. Went up later that day to find that the bed linen had been removed. When they left I had to re-tighten the bed and rewashed the linen again. Even after that it was about a week before I stopped sleeping in a sleeping bag on my bed. ;__; They've been up a few times after that but never again were they allowed to sleep in my room. >:
It never happened to me, but I did stumble upon a letter that wasn' t left there for me to find. Its content is forever burned in my mind. Heh, could be worse I guess, some of my cousins/friends didn' t hear anything suspicious beforehand and ... entered their parents room without knocking.