Conversation:

Joseph: "Mommy, are you skinny?"
Mommy: "What do you think?"
Joseph: "You are getting there because Samuel is out of your belly."
Mommy: "Yep, Samuel is out of my belly."
Joseph: "How do babies get in bellies?"
Mommy: (at a loss on how to explain the concept of sex without using techinical terms and thinking that her son is waaaaay to young for a sex talk pauses and doesn't know what to say) "They grow there." (Not a very good answer at all)
Joseph: "They grow there?!"
Mommy: "I will get back to you on that."

Now comes the research on how to explain to toddlers where babies come from.