Well I/we was watching a little bit of pornography (Young Harlots School Trip) and there was a 3 sum (MMF) with a girl that looks very similar to an administration assistant I worked with about a year ago… it isn’t her (I don’t think lol) but the similarity is very close, I had to do a double take… a bit of a shock
Anyone else ever thought they knew a person in a porno?
Yes. A redhead girl I watched in a porn movie few years ago looked exactly like a girl from my neighbourhood. I still don't know if that was her. 
A girl I went to school with did a photoshoot for some adult website. I can't remember who told me or how they found out but my friends and I searched for them and much to our delight, it was definitely her!
This has happened to me ... I found out while helping her out with a computer problem. Turns out she has a whole website and everything
Many many years ago (pre internet age) I acquired a top shelf magazine (remember those?) and thumbing through found the girls from section which that week was from my home town.
One of the young women featured was an old class mate from about 2 years previously, I occaisionaly wonder whether she continued or if it was a one off.