Father to one of my kids
A guy goes to the supermarket and notices a beautiful blond woman wave at him and 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 kids."
Now his mind travels back to the only time he has ever been unfaithful to his wife and says: "My God, are you the stripper from my bachelor party that got me so excited I had to lay you right there on the pool table with all my buddies spraying whip cream on us?"
She looks into his eyes and calmly says: "No, actually I'm your son's maths teacher!"