In Edinburgh, in 1984 I was in the same nursery school, then the same primary school as K. We met briefly and hit it off, but were never in the same class. Then she moved schools.
In San Diego, in 2004 or 2005 I started commenting on the blog of an Edinburgher I'd noticed in comments on a few of my favourite blogs. We had a lot in common, and eventually figured out that we'd met at age 4.
This year, in Edinburgh again, I met her Mum, who also reads blogs (a rarity, my parents know I have one, and as far as I know have never visited it, it's not their thing).
So the mother of my nursery-schoolmate whom I re-met through the internet...alerts me to a news article on my father's retirement (before my father does), and the article mentions there's a Facebook group of his students, and "appreciation society". Of course I go to join it, he's my Dad after all. The first post I find on the group's home page contains a Chuck Norris joke about my dad.
The internet is a wonderful, bizarre place.