What spawned this idea?
Most of those have been talked to death here, but you maybe asking "Night Court?" Probably because you never heard of it or barely remember it. Well, some blonde cunt from a network decided she wanted to be a Mary Sue, so her character became the here-to-fore unknown daughter of the Main Character, a common Mary Sue trope. The show is painfully lacking in jokes, the characters are all 2 cent copies of the originals without any of the soul or acting ability, and the shit just looks bad. During the preview, the bitch even mentioned it was her vanity project.
Then I saw the post about Phoebe walleyed-bridgefucker, and I realized she did the same thing. Mindy Kellogscornflakes did another Mary Sue trope, she corrupted the soul and possessed an already established character to the point they became an OFC Mary Sue. The writers of The Witcher and Rangz of Kangz did it too.
I'm becoming more and more of the opinion that the point is to hammer home that they're Big People and are allowed to do this to Little People - us.
It kinda fits in with the power politics thing they seem to go in for too. Getting your capricious whims imposed upon unwilling people is the definition of arbitrary power, is it not?