These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Pete: Is he a horrible person who deserves everything he gets, or a Designated MonkeyJerkass Woobie? Which side you fall on seems to rely heavily on how much of a Woobie you think PJ is and on how blameless you find Goofy.
PJ: How intelligent or unintelligent is he? Is he a generic stereotype of some sort or a very deep, nuanced character?
Peg: Is she reasonable with her anger about Pete, or does she treat him unfairly? This often relies on your particular interpretation of Pete as well. There is also a school of thought that suggests Peg's behavior toward Pete and Goofy indicates she's having an affair with Goofy.
Bizarro Episode: The episodes in which Goofy reads to Max the history of various ancestors. Aside from the framing device, there is nothing to tie these into the series continuity and they play more like Classic Disney Shorts than Goof Troop episodes, up to and including putting Pete in the role of a traditional villain in four of them. Peg and Pistol are also used in the stories but multiple times are given roles counter to their canonical characterization, Pistol's character is never related to Pete's, and PJ is not seen once in any of these episodes, story or framing device.
Designated Villain: Douglas from "Lethal Goofin'" attempts to buy worthless baseball cards cheap, then destroy all but one, jacking up its value...once again, his evil act was to legally purchase a commodity of no inherent value, then destroy his own property, creating a scarcity of something no one wanted.
Hilarious in Hindsight: In "Max-Imum Insecurity", Pete briefly mistakes PJ for Peg and grumbles about how his voice should hurry up and change already. While this is funny without hindsight since PJ isn't even a teenager yet, it's even funnier after the release of An Extremely Goofy Movie, where he is an adult and his voice still hasn't changed.
Jerkass Woobie: Pete sometimes fits this trope depending on the writer. Sometimes his karmic punishment can tread into Disproportionate Retribution, and occasionally he won't have done anything wrong in the episode itself, which can make him appear to be a Designated Monkey depending on what parts of the show you've seen. But most fans will agree that he deserves at least some of his punishment because he's, well, a Jerkass.
Love to Hate: Pete has a sizable fanbase of people who love watching him get his comeuppance. He is loved for being an antagonist with depth, realistic motivations, a number of relatable flaws, and a hilarious personality. He is hated for selfishly and dishonestly mistreating the two most sympathetic characters on the show on a habitual basis (and others on occasion).
Memetic Sex God: Peg, so very much. Or Pete, depending on your preferences. Then of course there's the realization that Goofy, at some point, had sex with a woman and conceived a child.
Misaimed Fandom: A group of fans whitewash Pete's actions by blowing his rare moments of clarity out of proportion and downplaying or ignoring his routine mistreatment of other characters. Not exactly the reaction you're meant to have to the Hate Sink.
Unpopular Popular Character: Max and PJ, when not portrayed as outright losers, are portrayed as not having a lot of friends. Due to their relatable personalities, Max's adorkability, and PJ's woobie status, both are quite well-liked in the fandom. Max especially, as he is easily the most popular second generation character in both the series and movies.
The Woobie: Poor PJ, having to live with a narcissistic bully of a father, repeatedly getting ignored or outright falsely accused even by his best and only friend, having bad things happen to him out of his control in most episodes where he appears, clearly being affected both immediately and in the long-term by his problems, and never doing a single thing to deserve any of it. Thankfully he gets a happy ending in the second movie.