I have a very similar story of an encounter at the park with my 4 year old identical twins. The other day, I noticed two older ladies sitting on a nearby bench, chatting away, while keeping an eye on my girls who were busy playing on the jungle gym. After some time, one of them called out to me, asking if "your grandchildren" were mine. I replied with a proud yes, feeling somewhat pleased that they could spot the resemblance. But then, the other lady quickly interjected, pointing at my children, "No, those are two different kids!" Turned out, my twins had done a switcheroo mid-play, and after observing them, these aunties were convinced that they weren't siblings because of their different hairstyles! I nearly spit out my water in laughter, and the ladies were so convinced of what they saw that they started arguing over it! Kids, hey?