That was a very famous incident, try searching "fischer nigel short bongcloud". Someone played several games against Short and won them all with horrible openings using 2 Kf2 and the like (not Ke2 iirc). The person knew some Fischer trivia so there was wide speculation (including by Short) that the mysterious opponent was Fischer himself. Consensus these days was that it was some prankster using an engine. This was in the era before powerful engines were that widely available, so they weren't people's immediate thought, but they existed.