When I was in high school back in the mid to late 1990s (between 1996 and 2000), my friends and I play-tested a fantasy role-playing game that one of them had received through the mail. The main conceit of the game was that you (the player) was pulled into a medieval fantasy world with nothing more than the clothes you were wearing right now and whatever was in your pockets. You made characters based on your real-life stats and skills. I don't remember much about the system itself. It may have been percentile based, but I also seem to recall that there were basic stats similar to D&D (Strength, Constitution, Charisma, etc.)
I don't know if it actually became a published product or not. It was definitely a separate system, rather than an adventure for another system.
Best Answer
Timelords (1987 for 1st edition, 1990 for 2nd) was another RPG that had the players generate characters based on themselves. It was not actually a fantasy game, but a time travel game. It did have, as a default setting, the idea that the GM had brought a strange new d20 to the game session, which turned out to be a timetravelling device. The device inadvertently activated during the session, and so the characters were placed into the ingame setting with whatever happened to be in the player's possession at the time (along with anything within a certain distance). The game posited alternate universes, and so could potentially have sent characters to some sort of medieval setting that would seem like a fantasy world.