My first year in the Corps (1992) I was in communication school in 29 Palms, California. One night we were at a party that took up about three or four hotel rooms out in town (I think it was the Hillside Motel). That night there was a huge earthquake centered only 10 miles away (I think it was this one:
http://www.data.scec.org/chrono_index/landersq.html.).
Four years later I was in Okinawa for a year. I became real good friends with one guy. We went to clubs together; we always hung out together; if I was going out with a girl, he'd go out with her friend, and vice-versa; we went half on a car to get around, ect, ect. We were like brothers. Anyway, after the year is almost over, I was telling him about the time I was at a party in 29 Palms and there was this big earthquake. It turns out he was at the same party - in fact me and him and a group of others had stood outside in a circle talking for about 30 minutes, and as soon as we figured out we were at the same party we remembered the conversation. All this time we had hung out together for about 10 months, and had never realized that we had been at one of the most memorable times in our lives at the same time. Also, it turns out the girl that I had hooked up with that night, he ended up dating about a year later. Biggest coincidence of my life.
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Another coincidence in the Marine Corps was that I was in the Quantico messhall (the one next to barracks 2005, for those who've been there), and I met one of my best friends in high school there. It turns out he had signed up just like I had, and neither of us knew that the other had joined the Corps.
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One more coincidence: I spent about 6 years on Quantico. I met my wife there. Anyway there was this guy who had dated my wife after we had broke up (we got back together a few years later). It turns out he also dated two other women in the same area, both after I had dated them, and in the same order as I had dated for all three. Me and this guy never had met until after the fact of all this. A couple of years later I was hanging out at one of the women's houses that we had both dated (me and her remained good friends), and he showed up to hang out, too (he remained good friends with her, too). Until that time we had never met. We were both in the Marine Corps, approximately the same age, dated all the same women in the same order, and we were even in the same battalion. We had heard about each other, but had never met until then. It was sort of weird, because I was thinking this guy would be a clone of me or something. He wasn't....we look very little alike, and have very different mannerisms. We got along okay, but it still felt weird talking to the guy for some reason.