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.
Awesome Music: The theme song used for the Stardust Crusaders OVA, a cover of "Holy Diver" by Ronnie James Dio (The first half of Dio's namesake), preformed by Killswitch Engage. The original is used at the end of Dio's proper debut episode as well.
When Dio pulls an Out of the Inferno with Senator Philip's body, the intro to "March of Mephistopheles" by Kamelot is used to startling effect.
Ensemble Darkhorse: Dio's hipster underlings steal the whole damn show, in the first PB episode.
Jotaro: Wow Dio, looks like I just violated your manhole..... cover.
Also gets lampshaded and defied when Dio's explaining what he did to Joseph.
Dio: I, Dio, blew any chance of him living out of the water. I, Dio, sucked him bone dry. I, Dio, reached around and— you're just getting me to say a whole bunch of really gay sh*t now, aren't you.
Jotaro: Heh heh, yeah.
Growing the Beard: Most fans agree that the series noticeably jumped in quality either on episode 4 or 6, depending on who you ask.
Harsher in Hindsight: Speedwagon after being hit by Zeppeli, states that he'll never have kids, which would explain things.
Hilarious in Hindsight: Speedwagon at the end of the comment special, commits that he has tanning oil in case of encountering half naked men. Years later, he meets the Pillar Men who all qualify for this.
Hilarious in Hindsight: The bonus video "Doppio was phone?" has a guy drunk calling Hirohiko Araki and asking if they would ever make another Jojo anime. It took two and a half years, but he got his wish.
Joseph's description of the picture he offers D'Arby is rather.... descriptive.
Joseph: That's a picture. Of me. Sitting on a couch. With my legs spread open. Naked. This picture was on the cover of GDILFs Magazine's 'Top Ten Sexiest, Most F*** able Grandpas. I was number one. Beating both Monkey D. Garp from One Piece, and Uncle Iroh from Avatar.
D'Arby: How...recent...is that picture?
Even more hilarious/disturbing is the fact that there really is a picture out there that matches that description quite closely, despite it being unlikely for Antfish to have inspiration for the joke from it.
N'Doul's death scene of all things, especially when the sad music starts up and N'Doul relates his tragic backstory to Jotaro. Sure it hits Mood Whiplash when Jotaro points out that said backstory was lifted from a flashback from Ray but it goes back to emotional when Jotaro buries him and wonders if they could have been friends.
An minor one in the Comment Special of all things. Dio's response to Jotaro's dig at the fact he has no real friends showed some serious insecurity. It becomes funny almost immediately afterwards, but it was clear Dio was actually pretty darn hurt by that observation.
Jotaro: You're a jerk...because you don't have any friends.