After 10 years, the wife starts to think their kid looks simply a bit too different, so she decides to do a DNA test. She finds out that the kid is actually from completely different parents.
Wife: 'Honey, I have something very serious to tell you.'
Husband: 'Yeah, what is it?'
Wife: 'According to DNA test results, this is not our kid.'
Husband: 'Yeah, sure. You don't remember, do you? When we were leaving the hospital, I had just settled you comfortably in the truck, when you noticed that our baby had pooped. Then you said: "Please go change the baby, I'll wait for you here." So I went inside, got a clean one and left the dirty one there.”
Moral: Never present a man with a problem which is not meant be solved in the most direct way by simple logic!