A few times over the last couple of years, I'll be standing in line at some food joint or coffee place at the University, and somebody will treat me, and then say something like "Pass it on!" (but not necessarily in so many words; the act doesn't seem to have a formula associated with it, oddly enough.) So a couple of days ago somebody treated me, and today I remembered pass it on. "Now you can do it for somebody else."
It's a nice little tradition, a "random act of kindness," and I haven't experienced it anywhere else, ever. Has anyone else?