A guy goes to the supermarket and notices an attractive woman
waving at him.
She says hello!
He's rather taken aback because he can't place where he knows her from.
So he says, 'Do you know me?'
To which she replies, 'I think you're the father of one of my children.'
Now his mind travels back to the only time he has ever been unfaithful to his wife and says,
'Are you the stripper from the bachelor party that I made love to on the snooker table with all my mates watching while someone whipped my bum with wet celery???
She looks into his eyes and says calmly, 'No, I'm your son's teacher.'
I've posted it here at least twice - once a couple of years ago and once about a week ago. But it's still one of my favourites. (But then I used to be a teacher.)