A lady I know who was in the original Acting Company was Patti's understudy in this show. She never went on until one day Patti was soooo sick she was going to have to. She rehearsed all afternoon, including, nervously, the famous nude scene where she had to make sure the wig hit all the right places, and was finally set to go on when, at the last possible moment, Patti lurched in, "insisting" that she was fine and could do the show.
My friend never did go on in the role. Patti's understudies NEVER went on, at least in those days.
Faced with these Loreleis, what man can moralize!