There are times in the show where MPB seems like he’s very emotionally mature, almost the voice of reason when talking to one of the characters. Then there are times where either the butt of the joke or just really good at playing stupid. From his word plays, to his scatter brained ideas with Todd, to the crew neck/v neck discussion with Bojack. I think it’s just hard to know how to take his character
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 are many different types of intelligence! We tend to only readily recognize a few of them.