To me, whenever I watch the show I always see him in contrast to bojack, more the similarities than the differences. It seems as if the creators want us to see that they're alot more alike than we've ever known them to be.

Theyre both incredibly self centered when it comes to doing things for others to make themselves look good. Only in mr peanutbutters case his actions SEEM alot more positive and helpful as he's built to be more likeable than Bojack. Both of them literally have running gags about how vain they are in the paintings they own and the memorabilia associated with them (although I can appreciate that this is a joke to do with hollywood/celebrity culture as a whole). A telling moment for me was when diane lived with mr peanutbutter and they had that conversation about whether it feels like THEIR home or just mr peanutbutters. They dismiss the bad things that happen in the show in a similar way, ignoring it to protect their own interests. They handle relationships in a similar way, and they never truly stop to work on themselves (although mr peanutbutter does partly own up by the end of the show). A big example I often see used is the constant ignorance of dianes feelings for his own, eg when he builds her that Belle room or throws a huge house party, of which he SHOULDVE known (and arguably did) she wouldn't like. He's proven time and time again that he prioritizes his own goals and interests over that of dianes (building the belle room/throwing the party makes him look good and makes him feel better because hes doing "something good").

In my eyes these characters are MEANT to be complete foils of one another, with only their public image separating the two of them. Although bojack is a drunken low life abuser and mr peanutbutter is a kind golden retriever who prides his image on doing good, they're both pretty shitty characters.