Surprise shared culture

I was sitting at a work going away party with D___, who divided his spare time between getting stoned in front of the telly and going raving, and M______, who is a Girl About Town, when the indie disco that we just barely hear downstairs started playing "Where's My Jumper?" by the Sultans of Ping. We all started nodding our head to the fairly disctinctive beat, and at the verse sang (shouted) as one "My! Brother! Knows Karl Marx!"

One that springs to mind is when the conversation at work once turned to the Marx Brothers, and a quiet new guy to whom I'd barely spoken was the only person able to answer my trivia question about who the fifth brother was.