I have a couple. I was about one month into a new relationship and for some crazed reason I volunteered to cook a fancy meal for this guy's best friend and his wife. I knew they were snobs, kind of like my new bf, but I did it anyway. Things were going quite well. I had just served the main course and we were about to tuck in when the dining room ceiling start disintegrating. Bits of plaster, etc. were coming down fast and furious. We'd all just stood up and moved away from the table when water started pouring down. Turns out my idiotic upstairs neighbour had left the tub running!
Dinner was over, and so was that relationship. He had absolutely NO sense of humour so good riddance.
Another time was a bit more convivial, although I didn't know one of the couples. They were friends of friends. We were sitting around at the table before dessert talking and drinking wine when my Siamese cat came bounding in looking very pleased with himself. The woman I didn't know coaxed him over -- he wasn't that friendly to strangers -- only to discover a bloody tampon hanging from his chops! I know...I discovered too late that this particular cat had a thing for garbage and tampons.
There was a bit of shocked silence then I started laughing and everybody joined in except for this woman who turned into a total pill. She and hubby left shortly afterward. I've dined out on this story for years, and I get mixed reactions to it to say the least!