Great story though.
Another time when my previous mother and father in law were staying over, and we gave up our bedroom for the the night after a drunken party, I got up, bollock naked, and went for a slash. When I got back into the bed and heard.. 'Jim, there's someone in the bed,' I thought how thin the walls must be. Jim answered 'That's me, you daft woman!' and that was followed by 'No, on the other side of the bed!' That's when the penny dropped.
Rather than just declare it was all a big mistake, I slid out of the bed and crawled on my hands and knees towards the door. As I was about to pull it open at the bottom the light came on and there stood Jim. 'What the hell's going on?' he demanded. I stood up, covered my naughty bits and explained it was force of habit that led me back into our bedroom. It certainly wasn't lust that led me there, I may have had my beer goggles on but even then my mother-in-law had a face like a bag of spanners!