Well, don't tell my son I am posting this but he was an early talker and you really had to watch. When he was three he walked up to a greeter in Walmart (who happened to be a little person) and asked "Why are you a midget"? I wanted to DIE!
Then a few weeks later (he was on a roll) we were at a Chinese buffet restaurant and he was watching a woman really intently. After a few minutes he turned around and said "Mom, she already had seconds. Her needs a diet". She was a rather large lady and heard him. Again, I wanted to crawl under the table.
Through the years he has thankfully learned to keep such thoughts to himself or at least wait till we are out of earshot