I've heard this quite a few times. It pissed me off every time.
It's usually said in a condescending tone that makes me want to Ric Flair chop the person that blabbed it. If I'm not smiling, there is a reason for it. So mind your damn business.
I digress.
Anyway, a few weeks ago I placed two clementines on my desk. On one I drew a smiley face and on the other I drew a frown. (For no other reason than I am a child.) Little did I know it would turn into a scientific experiment of epic ...