After ten years, the wife starts to think their kid looks kinda strange, so she decides to do a DNA test. She finds out that the child is actually from a completely different set of parents.
Wife: Honey. I have something very serious to tell you.
Husband: What’s up?
Wife: Well, according to these DNA test results, this isn’t our child.
Husband: Oh, you don’t remember, do you? When we were leaving the hospital, we noticed that our baby had pooped. Then you said, “Please go change the baby. I’ll wait for you in the car.” So I went back inside, got a clean baby and left the dirty one there.