Smile, it might never happen
or
Hey, you look like a lovely girl, why not give us a little smile, heh?
I originally thought this was just the Glasgow males lack of imagination, the fact that you'd hear comments like that passed to women in bars and night clubs almost anywhere you went and any night of the week. Then I travelled about a bit and let me reassure you, it's everywhere.
It translates into other languages. Men even use hand gestures when all else fails. And it even extends to same sex encounters. I've been told to smile whilst sitting on my own at the end of a bar. Or asked if there's something wrong, after all you look so sullen. I'm quite happy sitting on my own, thinking, I just don't have a requirement or want to grin like a maniac whilst doing so.
It's not that you have to be unhappy not to smile, smiling takes effort. I know this, the number of times I've heard 'smiling is a form of exercise, it burns up calories' or something similar...
The one time I did smile was on hearing someone try the Smile, it might never happen line on a friend I was out at a bar with.
"I've been doing that all night and quite frankly my jaw aches" she retorted.