Inspired by a conversation I was having with GC earlier, and also by the student Oldspice mentioned who thought Devon was in London. Who has come into contact with a dopey tourist - e.g. wanting directions to London from Scotland as if they could walk it?
I once heard these two Americans discussing Wales on a train. One had never heard of it, so his friend helpfully told him 'it's a suburb of Birmingham, it's kinda pretty...'
Another classic was when I was on holiday in Gran Canaria a few years back. One of the reps told me a traveller had asked where she could catch the bus to Tenerife from. Upon being told she would need to catch a boat, not a bus, she became very annoyed, shouting 'well I was told I could catch a bus, so where do I catch it from?', despite being repeatedly told it was a different island!