Art's discovery.

Last night Art was taking a bubble bath. His hand was under the water and he looked up as if he made a real discovery.
"Papa, there's a ball in my penis!"
I tried to contain my laugh. "Yes, it's actually called a testicle. You have two of them."
He thought for a bit. Then, delighted, he looked at me hard just to make sure I wasn't kidding. "I have two of them!?"