A man was standing in the queue at the check out in Tescos when a very attractive woman behind him said, "Hello!"
He gave her that "who are you look," and couldn't remember ever having seen her before.
Noticing his look, she figured she had made a mistake and apologised. "Look," she said "I'm really sorry but when I first saw you, I thought you were the father of one of my children," and walked out of the supermarket.
The man was dumbfounded and thought to himself, "What is the world coming to? Here is an attractive woman who can't keep track of who fathers her children!"
Then he thought a little... "I don't remember her," he thought, "but, MAYBE... during one of those wild parties I went to in university, perhaps I had fathered a child!"
He ran from the supermarket and caught up with her in the parking lot, "Are you the girl I met at that university and we got really drunk and had wild crazy sex in front of everyone?"
"No!", she said with a horrified look on her face. "I'm your son's SCHOOL TEACHER!"