I'm kinda butting into this forum, but I saw the thread title on the main page and I have a couple of stories to share. Most of my painful ones are from adults or teens, so these are just cute ones.
Last summer I was out running, and I was doing the couch-to-5K program which involves running and walking intervals. I ran past two sisters, probably 4 and 6, when I was near the point where I turn around and head back. On my way back, when I was across the street from them, it was time to stop running. The little one asks the older one "why is she walking now?" and the older one says "she runs then she walks then she runs again, because she thinks she's fat and she wants to get skinny." I cracked up... it was too cute, and absolutely true!
When I was pregnant, years ago, my little cousin said to me "wow, you got fat!" Then she realized it might sound rude and said "I don't mean you're always fat, I know it's just because of the baby." That one still tends to put her foot in her mouth at age 15.