My son (at age 6) to my wife after playing with a Down's Syndrome boy:
"So, um...  was he Russian?"

My son (at age 4) learning to play 20 Questions:
"I'm thinking of something with no hair.  Like you daddy."
"I'm thinking of something big.  Like you daddy" as he rubbed my belly.

My two sons talking:
(7 year old): You never give any alone time.  I need alone time!
(5 year old): Yes I do!  Remember before I was born?