Tiny, tiny people

Our cat is being neutered next week. 

This evening I attempted to gently explain to five year old Darius what "neuter" means using words he already knows.  I said, "Just like you, Freddy has a penis and balls.  We'll take him to the doctor and he will perform a surgery that removes Freddy's balls.  That way, he won't be able to make baby kitties if he meets a girl cat."

I was trying to tread carefully here, as he is not my child and it is not my place to have his first birds and bees talk with him.

"Why doesn't he want to make baby kitties?" he asked.

"Well, I don't know if he wants to or not, but we don't want him to.  That's why we are taking him to the doctor," I answered.

He looked thoughtfully at Freddy's rear end.  "His balls let him make baby kitties?"

"Yes," I explained.  "Just like humans can make baby people, cats can make baby kitties."

His eyes widened.  He reached down to his Batman costume pants, lifted up his own testicles, and said, "You mean there's tiny people in here?"