Who's wiping whose bottom?

I was wiping Ulysses's bottom when he said to me, "Mama, I don't want to be a little boy."

"What do you want to be?" I asked.

"A big boy."

I was silent for a moment. Then I said, "You're getting bigger every day."

"Bigger than you!" he said.

"You say you're bigger than me?" I asked.

"Yes, I am!"

I thought about that. "You know, big boys wipe their own bottoms."

.