The Studio System and the Golden Age of Hollywood - there are lots of tales and stories that came out later which, if known by the general public back then would most likely have caused an outrage. Open secrets in Hollywood about LGBT folks or even those who didn't mind experimenting with same-sex activities at times, arranged relationships and more or less forced marriages, child actors being given "pep pills" or "special vitamins" which were actually addictive drugs that allowed them to work long hours and eventually led a number of them to a life of drug addition. There were houses of prostitution on the MGM lot where Louie B Mayer would send some actors so they'd have 'bragging rights' if their manhood was at all in question. Several actors were drunks and were hell to work with on some movie sets, there'd be fistfights over top billing or who's name was on top on posters and during during opening credits, some actors would actually count the number of lines spoken by various characters so they could ensure they had the most, and the stories go on and on. In many cases I'd rather not know the true details of what went on behind the scenes while filming some movies I really enjoy as I'd rather somewhat innocently enjoy them, especially the ones featuring actors that are no longer with us, vs. knowing some of the true stories and character flaws of the actors involved.
Others, of course, can be fascinating and even offer up lessons to be learned from.
