When people at gatherings and parties etc., ask how my wife and I met, I like to go into this elaborate lie where I say that, albeit I was a stranger, I was a kidney donor who matched her then husband's blood type, and was a perfect match.
I then go onto say how I decided not to donate the kidney, and, instead, we embarked on an affair while her husband, unaware of all this, was in intensive care. We eventually married after he died of kidney failure and, added bonus, she got the life insurance.
It really is a conversation stopper if you don't want to talk to the nosy cunt who asked in the first place.