I see London, I see France, I see _____’s underpants!
This is a popular rhyme amongst children and my informant remembered that he used to say it all the time. When they were either playing a hand clapping game or even just jump roping, the kids would sing this tune and pronounce that they saw so and so’s underpants, even if they happened.
I believe that sexual humor is always prominent no matter what the age and is especially getting more prominent in today’s culture. I remember boys would say this to girls in grade school and then chase them down to kiss them afterwards.