Was stood in the (huge) queue at Birmingham Airport on my way to Malaysia three years ago and someone from security opened a barrier up which I went through. Some seriously ripped bloke had a right go at me for pushing in, which I pushed back against, following which his girlfriend intervened and stood up for me and put him straight as she’d seen what had actually happened. After we’d all made up she clocked my sweatshirt which was for my maté’s business in Nottingham (which I was wearing for the flight because it was ridiculously comfortable) and over the course of the next ten minutes we realised that we must have about 50 friends in common in Nottingham, and she used to work in one of my other mate’s businesses for a few years, to the extent it was actually a bit weird that we’d never met before.
It’s not the most unlikely of coincidences on this thread, given the geographical proximity, but it was the totally random nature of the interaction and the fact I was wearing that sweatshirt that made me think about it so much on the flight afterwards.