James Brown and Richard Prior were always on drugs. I'm not so sure about Crispin Glover. He was in character.
Back in the 1970s, I remember watching the Wide World of Sports, or something like that, when this stuntman was strapped to the top of a commercial airliner during a flight. After the stunt, they tried to interview the guy, but he was so heavily drugged that he couldn't speak. Does that souond familiar to anybody else?
Well thats not fair! I believe anybody would do a stunt if they were too F-ed up to know what was going on. Give a man some angeldust and you will see some stunts.