A series of fucked up life stories. Wrongs choices been made, then live with them with humour. Trying to escape? There it is, another wrong choice. Bojack and Mr peanut butter represent the two opposite attitudes of life.
I think it's great that they are not making BoJack "just the douche" character. Backstories help a lot but it's also just about setting up the scene: can people be good in the environment? What are the motivations, challenges, triggers, and obstacles? Who defines happiness?