I think like everything in the show it’s nuanced. He’s supposed to be a completely oblivious aging white male celebrity. He can never fail in a way that ends or damages his career. Cheating on pickles means he lucks into being the face of depression, his bankrupting spaghetti strainers save the day. He’s not completely untalented (Diane compliments him for Philbert) or malicious (forgives bojack on his show, nominates bojack for Oscar) but I don’t think that means he’s hiding some deep intelligence. He also acts selfishly (Cordova/Hank saga) and feeds into his own delusion (angry with Diane about questioning relationship with his brother, denial about dead mom and dad).

The show portrays a lot of different ways of dealing with relationships and weighs pros and cons of each. PB struggles with personal relationships and maturing but his happy go lucky “can-do” and forgiving attitude has value in situations with Diane and Bojack who so often feed into depression and pessimism. It’s important that someone can forgive Bojack (offers to house him post prison) and Diane (hiding out with Bojack) unconditionally, even if we see how that can negatively effect PB in the long run.

Diane and PB’s phone conversation in season 6 encapsulates this all really well. Sorry for long form analysis I have autism and an English degree.

I think this relates to Diane’s “I don’t really believe people have a ‘deep down’” speech. He is exactly what you described, a goofball who’s good at making corny puns and is occasionally very incisive about how people relate to each other. He’s not self centered exactly, but he does whatever is going to make him happy, and avoids over thinking things. He likes positive attention so he comes off as a lot nicer and considerate than Bojack does. That’s his whole friction with Dianne, that the things he does for her aren’t really for her, they are to keep her attention on him, and that makes him incapable of really nurturing other people. I think that’s why he’s so desperate to be friends with BoJack, why he’s the one who picks him up from jail to go to the wedding. He see’s how similar they are in that regard.

He’s not smart, he’s clever. He’s just a mechanism that happens to extremely well suited for his environment. He doesn’t have to be introspective, there isn’t a secret plan or calculations about appearing dim to put people at ease. He just does what feels right and it works out for him, kinda. Like his whole relationship with Todd, they spend a ton of screen time together but they aren’t really friends in any meaningful way, hell their is an explicit joke that their relationship is just "Yes, and"ing each other.

Man even the V neck vs crew neck discussion fits with this. It’s not a big deal to him because he’s worried about his visual portrayal, it’s important to him because he likes things that are comfortable, he finds V necks comfortable, so his character should be wearing a V neck in the movie. Simple as.

Neither. He is avoidant AF, and avoids introspection as part of that. He is a social butterfly but he lacks the self reflection to have truly fulfilling close relationships.

I’m not sure why this scene comes to mind and I don’t remember it exactly but I always felt like the scene when bojack is at the game show and PB kinda goes off at him for kissing Diane is like the only time we really see a side of PB that doesn’t feel forced.

I think what it is is that it shows he does do critical thinking and reflects on stuff but just chooses not to say it

He doesn’t need to be smart because everything just falls his way.

He’s a DOG.

I know this is just a tv show discussion but, I stopped thinking of people in terms of smart and dumb. Some people are smarter than others but everyone has something. Mister Peanutbutter is carefree, a little oblivious but not stupid.

There’s a great, thorough description of him here: https://bojackhorseman.fandom.com/wiki/Mr._Peanutbutter#:~:text=Peanutbutter%2C the star of Mr,main characters in BoJack Horseman.