We were staying at her mothers, and I'm convinced her step-father was watching us through a partially open door having sex one night.
I knew he was watching so I did my best to make it interesting. I had her strip for me and suck my cock, gave her a good oral orgasm, and then flipped her over and hammered her from behind. She was oblivious (until I told her in the morning), but enjoyed every bit of of it.