I think one of my favorite things that I recently did while on BART was this:
I was minding my own business when fifteen or twenty college kids got on the train, obviously they were really new to BART and really new to the bay area, and one of them sat down next to me and introduced himself to me right off the bat. I was just commuting or going someplace normal, and he seemed like he was just excited to be on a train, so I mumbled something and went back to my book. The kid’s name was Jimmy, and Jimmy didn’t know yet that it’s not standard operating procedure to introduce yourself to ever seat-mate on public transit.
Anyway, four or five stops went by, and it was time for Jimmy and his friends to get off at downtown Berkeley. He walked out, fifteen or twenty excited kids got off, and I a bell went off in my head. Something compelled me to stand up and walk to the door of the now empty train, and I shout right at him through the crowd, “HEY JIMMY!!”
He had a shocked look on his face as he looked at me, and all of his friends looked at me, and then looked at him, and back at me, and back at him, trying to discern why I knew his name and was yelling for his attention. So, with no further explanation I maintained my grinning eye contact with Jimmy and gave him a huge thumbs-up and a knowing wink as the train doors closed. I assume that his friends badgered him for the rest of the night, asking him what that was all about and who I was.