The infamous "DUWANG" Translation Trainwreck of part 4 has brought some memorable lines such as "Get a feeling so complicated...", "Who in FACE are you?!" and "What a beautiful Duwang". The improved translations in the making keep a few of those as in-jokes and the TV anime is being "translated" in this style.
Whenever an argument about who would beat whom in a fight comes up, the answer is always Giorno. Along with The Flash, he's perhaps the person most commonly brought up in power level debates.
The series' distinctive art style has become a meme, being a popular choice for Art Shifted fanart of other series.
Similarly, if someone randomly throws around the Japanese "dramatic tension" Unsound Effects ゴゴゴゴゴ (GO GO GO GO GO) and ドドドドド (DO DO DO DO DO), it's guaranteed to be a JoJo reference.
Araki's habit of drawing the characters in very weird poses such as Diavolo's final pose (when he's running from the little girl), Giorno's "gang-star" pose, and Anasui's model-esque◊ pose, has also spawned some memes.
Fans have noted a fair number of coincidental similarities between Part 2 and the movie Zoolander (if Joseph is Derek). The main character's lack of common sense in many areas, the rivalry between Joseph/Derek and the new blonde ripple user/model that comes on to the scene, the large emphasis on posing, the odd fact that some scenes just look familiar, and the fact that both characters had their friends killed by Wamuu.
"Giant bara deer": A term for the musclebound men in the first parts of JoJo that arose after this animated .gif of Jonathan◊ appeared on /a/ with the filename "giant_bara_deer_caught_in_headlights.gif".
Calling Wamuu's Holy Sandstorm attack the "Holy Wubstorm", after the Pillar Men's dubstepleitmotif.
Esidisi's crying face.
Rohan's response of "But I refuse/Daga kotowaru/だが断る" when Highway Star commands him to call Josuke for help and thus lead him into a trap, is also a popular meme in the Japanese community. Mainly because Rohan says that he likes saying "NO" to arrogant people's faces.
AWAKEN, MY MASTERS!/MEZAMETAMAE, WAGA ARUJITACHI YO!/目覚めたまえッ！我が主たちよ!Explanation Wamuu shouts this line when waking up two Pillar Men, Kars and Esidisi. What makes this moment is both Akio Ohtsuka's delivery of said line and the FABULOUS poses the three Pillar Men take once they're awakened, the fact that Wamuu awakens them by making his own fabulous pose while poking their cheeks with his fingers, and in the anime, the dubstep-laden music (Fittingly titled "Awake") playing over it.
Ahh! Sto-sama is dead!/あーん!スト様が死んだ! Explanation with mild spoilers for Battle Tendency Japanese meme taken from a fan-submitted picture of the slightly unhinged artist bawling on Straizo's chest at the end of the volume in which he dies. Likely kicked off because of the hilarious FangirlSelf Insert going on, and goes to show you that Estrogen Brigades as we know it (and the Draco in Leather Pants aspect of Fan Dumb for that matter) predate the Internet by a loooooong shot.
"The first time I saw her, with her hands on her knee...how do I say this...I had a boner..."Explanation Another Duwang classic that is rapidly gaining steam: A delirious and badly beaten Yoshikage Kira explains to a random woman about how he got an erection just from looking at the Mona Lisa which is why he kills women and takes their severed hands as "girlfriends." Even crazier is how accurate this is to the original Japanese, as the original panel has the kanji for "erection" inside of that very same speech bubble.
"Your stand is like your asshole. You can't go around showing it off to other people." Explanation A vulgar analogy used by Norisuke while talking to Josuke. It has been passed around on Tumblr to a dizzying extent.
Goodbye, JoJo! Explanation Dio has a propensity for Gratuitous English in the 2012 anime, and delivers the line with some pretty awkward pronunciation and emphasis.
"You thought this would be [X], but it was I, Dio!" Explanation Another Dio classic. Originally, it was a boast to Erina about stealing her first kiss from Jonathan during the start of Phantom Blood. The phrase got so popular that it's used as a punchline for a Bait and Switch joke for just about everything.
Diamond is Not Crazy Explanation A shorthand way of referring to the legal-dodging renames in the English version of All-Star Battle, in the shape of Part 4's Engrish-y name; specifically, to Josuke's Crazy Diamond having its name changed to Shining Diamond.