I just noticed their friendship is based on their traumas. Bojack had an horrible mother that never loved him And princess carolyn never been able to have a child. Princess carolyn always took Care of bojack in a somehow motherly way.
I kinda think bojack Sees her as a mother figure idk ?
PC also cares for Bojack the way she cared for her own alcoholic mother. They’re co-mommies to each other.