my dad has a ton of these "small world" stories. him and one of his brothers moved into an apartment that these two guys were leasing in steamboat when they were out of high school, but it was a dry year so they decided to move to hawaii after a couple months. In hawaii they met up with another brother (there's six of them) and told them the steamboat situation how they leased from these two guys. Fast forward 8 months and the hawaii brother is in spain about to do running of the bulls and he starts talking to these two guys in the group and it turns out to be the two guys that my dad and the first brother had rented the apartment from back in steamboat.
Another one, one of my dad's roomates when he first got out of college went to france for a year. One day she was at a super busy cafe and there was only one seat open in the whole place so she asks the girl sitting there if she can join her and they get to talking and it turns out that the girl is one my dad dated back in highschool.