Maybe not that obscure, but...
Years ago, in about 2010, I was on the way home from a camping trip in Cornwall with my parents. On the way back we decided to stop in Wells in Somerset because, as my parents said, they'd never visited the place before and wanted to have a look around. Anyway, we parked up at the cathedral and got out of the car for a look around. We were walking down Market Place in the middle of the town, heading south, and I had this really eerie feeling that I'd actually been to Wells before. I started asking my parents if we'd ever been on holiday when I was really small and they'd just forgotten about it, but they both repeatedly insisted we'd never been. We went in a café on the main stretch near the cathedral and grabbed some lunch, and all this time I was trying as hard as I could to remember bits of my life when I might have somehow ended up in Wells without my mum and dad. I couldn't think of anything and it was driving me mad, to the point where I honestly barely ate the sandwich I'd asked for. We left the café and started to head back to the car, heading northwards up Market Place and back towards the cathedral. And then it hit me that I was standing on the actual set of Hot Fuzz, and that they'd used Wells for the fictional Sandford village in the film. I'd watched the film so many times that, when inadvertently standing on the set, I started to believe I'd actually been there. When it clicked I started laughing out loud because I'd literally watched Hot Fuzz (for the 10th time) on the camping holiday we were coming home from, on a shitty little portable DVD player we had in the tent.
I've got a couple of other stories but that's absolutely the best one.