Man who claimed to have played Kong
In the 1970's a man named Carmen Nigro came forward with a widely-publicised story that he had been a professional "ape-suit" actor in Hollywood in the 1930s-50s, and that he had actually played Kong in certain scenes where stop-motion models weren't used. He was denounced as an attention-seeking fraud by film historians and the surviving cast/crew of King Kong. Sounds like a good subject for a documentary.
https://www.google.com/search?q=carmen+nigro+king+kong