One that sent spooky shivers up my spine...
Woke up one sunny Saturday morning, a London spinster with no plans. On the spur of the moment I just left the house, not knowing where I was going to end up. I started driving south from central London and ended up on the A3 and on there saw a sign for Brighton, and thought, yeah, I'll go there.
Got to Brighton, parked up and walked to the beach, which was thickly crowded with thousands of people. Picking my way through, trying to find a tiny patch of shingle to lay my towel, I saw a woman who was the spitting image of my mother. I was so fascinated that I approached closer, and to my utter amazement found it WAS my widowed mother, who also lived in London, and who I had not spoken to for a couple of weeks.
Neither of us had EVER spoken of going to Brighton (or anywhere else) for a day trip, weekend or holiday. She had never been there before, had never gone alone on a day trip anywhere, and she wasn't a spontaneous type of person. She'd got up that morning, seen a sunny day and on the spur of the moment went to Victoria station and caught the train to Brighton.
Even if we had both known the other was going to be there, the odds against finding one specific person in a crowd of thousands were millions to one against.