Interesting facts about the people 'behind the scenes' of Kpop? (Coaches, Managers, Stylists, Dancers etc...)

I just learned that Blackpink and Twice have the same vocal coach apparently...which is SUPER interesting to me

I also recall a really touching clip where it was revealed that Exid's manager, Jaehyun, stayed and worked with them without being paid at the very beginning.

Any other facts or tidbits about idols' managers, stylists, coaches, choreographers, back up dancers, etc.. that you guys can think of?