Something similar happened to me and PlaneMad (Arun Ganesh) in Mumbai. I was wearing Pune T shirt and him Mumbai T Shirt, and the person serving us food from the canteen was having fun reading the word 'Wikipedia' in the languages he could read (Kannada and Hindi, I believe?) - he could not read the english. Arun spent a while explaining Wikipedia to him, a conversation I was not able to take part in because of my lack of Hindi knowledge (sigh).