This little riff (-raff, ha) has been something stuck in the head of myself and a few friends of mine for many years- since high school, really (so, about 8 - 10 years).
I don't know how it happens, but something will set someone off... and then suddenly, someone is singing- yes, singing...
"Riff-raff"... "street rat"... I don't buy that... if only they'd look closer... would they see a poor boy? No, siree! They'd find out, there's so much more... to... me..........
Usually once someone starts it, it will be finished, no matter where we are. We have no shame to randomly burst into song in public. Like, one time we were in a mall... once it happened in a Walmart.