Having traveled a lot when I was younger, I experienced several "It's a Small World" situations.
One time, during a high school sponsored trip, I was walking with a friend along the streets of London, England. My friend (who was older and loved to try to pick up absolutely any girl he could) would say hi to every girl we passed. One time, we passed 2 British girls ... as usual, he said hi to them as we passed ... and as we kept walking, a voice said, "Hey - I know you!". It turns out they had met at a campground near Turkey Point, when she visited Canada the summer before.
Feel free to share your "It's a Small World" stories ...