You pick up a hitchhiker, a beautiful girl. She faints inside your car so you take her to a hospital.
At the hospital , they say she is pregnant & congratulate you that you are going to be a father.
You say that you are not the father, but the girl says you are.
You request a DNA test to prove that you are not the father.
After the tests are completed, the doctor says that you are infertile, and probably have been since birth.
On your way back home, you think about your 3 kids at home.