Same girl, separate instances.

The first one my girlfriend wanted to have sex in a "public" area - which, in hindsight, wasn't a very public area (it was my apartment's second floor porch) and we were on my airbag under my sheets and comforter - but I just couldn't do it the second a group of other college kids were passing us. She thought it was hot and funny and kept trying to keep me going as they passed.

The second time it was with my sister in the opposite bed while a movie was playing in a hotel, this time it was me being way too horny for my own good - this time I was the one who initiated - started fingering her and she kept trying to stop me but for some reason me shushing her made her stop trying to stop me. I have a good feeling that my sister knows what was happening since she kept forcing herself to physically silence herself but it's still a funny memory.

Obviously nothing crazy but still good memories.