This happened years ago, when I was in my Purty Thirties, at our son's Little League game.
We were sitting in the bleachers and I looked down the line towards first base, where our son was headed. When he got there, I started to look back at home plate but caught a man down at the other end grinning at me, so I smiled back. He was wearing a hat that said something, but I couldn't make it out, so I smiled again and turned back to the game.
Well, in the course of your son's Little League game, you look towards first base quite a few times, and each time I did, this guy met my glance, and I looked at his hat, trying to make it out, and he grinned at me, and I smiled back because I'd been caught staring at him and his hat. This little scenario repeated itself every little while for the whole game, he smiled, I squinted at his hat, I smiled.
Eventually the game broke up and the bleachers started clearing out. The man with the hat came closer, and finally I was able to read what it said:
"Smile if you're not wearing panties."