A man is driving up a steep, narrow mountain road. A woman is driving down the same road.
As they pass each other, the woman leans out the window and yells, “Pig!”
The man immediately leans out his window and replies, “Stupid cow!”
They each continue on their way, and as the man rounds the next corner he slams into a pig in the middle of the road.
This joke is included in the Black Book of Jokes. You can order it from here.