JoJo's Bizarre Adventure/WMG

JoJo's Bizarre Adventure

The frog Doppio ate after his battle with Risotto is the great grandson of the frog Zeppeli punched in part 1

 * Not possible. Frogs don't live as long as humans do, so if the frog Doppio ate was a descendant of the frog Zeppeli punched, there would be far more generations in between-the frog Doppio ate would more likely be the great-great grandson of the frog Zeppeli punched, if they're related. On the other hand, Ripple and Stand users age slower than other members of their species, and we do know that animals can have Stands...

Toshikazu Hazamada suffered a similar fate to The Twits
Think about it: the first time we saw him, Toshikazu was about as tall as Josuke. The next time we saw him he was only slightly taller than Koichi, and then after that we never saw him again. The reason for this could be that he's been steadily shrinking, until finally he got so small he winked out of existence. A possible explanation as to why Toshikazu shrunk is that one of the street punks who beat him up had a Stand power, similar to that of Little Feet.
 * I distinctly remember him among the gathering of Stand Users at the close of "Diamond is Invincible".
 * "One of the street punks"? No, my friend, everything that was needed was a visit from Josuke to the hospital. One that ended with him getting very pissed off at Toshikazu and "fixing" him up good.

Okuyasu is a Time Lord
Despite having an incredibly strong Stand, along with powers of space manipulation (logically making him only slightly less powerful than Dio)), Okuyasu doesn't win a single fight in the whole series. This leads one to believe that he may be a pacifist of some sort, and always allows his opponent to defeat him purposely so they can feel good about themselves. It also explains how he managed to  during the final battle against Yoshikage Kira.

Leaky-Eye Luka's shovel was his Stand
...Called the Ace of Spades.

In part 7, Steel Ball Run, assuming the Jesus foreshadowing is a red herring, then the corpse parts belong to either Santana or Cars
This is also assuming SBR is the world after Stairway to Heaven went off in part 6. The process tore one of them, likely Cars, apart. Being an immortal being, Cars still survived somewhat. The way the corpse parts merge with humans is reminiscent of how the Piller Men could eat humans. That SBR is an alternate Part 1 would match Cars reunification being an alternate Part 2.
 * Mirroring the end of Part 1, Johnny will lose his body to either Dio or the Saint.
 * Also, now that there has been an apparent immaculate conception in Lucy Steel, this could lead to the birth of Cars.
 * Now with Mangenta Mangenta's "death",This troper is less willing to believe Cars has anything to do with this immaculate conception.

Joseph of Arimathea will turn out to be a historic Jojo
Why else would he have been brought up by name?

Gyro's not long for this world
Let's face it, the Zeppelli bloodline is not well-known for their long lifespans once they encounter a Joestar. Also, in Chapter 2 Johnny notes that Gyro was a mystery "from beginning to end". It could translate either as the end of Part 7, or the end of his life. First time I read through I translated it as end of his life, given the track record of the Zeppelli family.

Giorno is still around
Gold Experience Requiem kept him from being Reset Button'd, but it couldn't do the same for anyone else. Plus Araki made some comment in Stone Ocean that Giorno "might be in Florida", why would he make such a comment if Giorno wouldn't ever show up ever again? ... of course this is probably wishful thinking.
 * Well he is a son of Dio.Maybe he was being recuited but turned down the offer.

JoJo is a creative retelling of Araki's real-life bizarre adventures
Araki regularly fights vampires, immortals and people with insane powers all the time when he's not writing crazy awesome manga. Stand Users and Ripple Warriors also age slower than normal humans, and Araki doesn't age.
 * By that logic Bruno Bucciarati is Tetsuya Nomura.

The Ripple is an early form of Spiral Energy
'Cause of... uh... the patterns they cause, and... er, it'd be neat? (I should have written more on this when the idea first struck me. Bother.)

The Stand can manifest itself by the rage of a pure heart, like the Super Saiyan
Jonathan Joestar had his own Stand, a very short range one -- and so a very powerful one. This troper guesses that its power is something like fortify all the Joestar's bloodline to inherit Jonathan's force of will and body. I'm not making this shit up! It can be seen here!
 * So its name should be Father Abraham, having a deepful meaning and also starting the musical groups Shout-Out.

Diavolo is the son of DIO.

 * Dio sneaked in to the prison with the World to conceive a powerful minion for future use. Also he conceived Ungaro Rykiel, Donatello and Versace at the same time.
 * Err - Dio wasn't exactly around to do this at the time. Furthermore, Diavolo was the one who originally discovered the Stand arrows, meaning Dio would not have The World at his disposal.
 * He could, however, be a descendent of Dio, probably from some mortal dalliance. Unless JJBA Vampires can have babies when they aren't attached to a not-quite-vampire body.

Dio never had a chance of becoming as strong as he once was after Part I.

 * And it was Enya's fault, because she unlocked  and Dio became too reliant on it. Even without that Stand, Dio was using Jonathan's body, and as such, was restricted with what he could do, no longer having his own body. Freezing blood, for example...
 * It's implied that it is because the neck scar wasn't fully healed yet, meaning that his head and Jonathan's body weren't fully synced yet. It is likely that the reason he was so determined to feed on the blood of the Joestars is because that was the only way to heal the scar. Supported by the fact that he became significantly stronger and his timestop increased only after he drank Joseph's blood.

Dio had kids to better synch with Jonathan's body.

 * If Jonathan's grandson gave him such a big boost, imagine what would have happened if he drained Jonathan's biological son instead. Or three of them, as the case may be. It would also explain why he didn't seem to give his henchmen any orders to take Joseph alive. Being able to drain him then was a happy accident, rather than his main goal, and he already had his main plans well underway by that point.

Dio Brando is still alive, and is in fact Santa Claus.
The only way Santa Claus could be able to travel all over the world in one night is if he either A) can travel in time or B) can stop time, and since there are no time travellers in the JJBA universe, it must be a time stopping ability. Because Jotaro is limited to stopping time for only 5 seconds, that means that Santa must be Dio under a clever disguise. It also explains why Santa only acts during the night: As a vampire, he would be killed by sunlight. Dio survived his battle with Jotaro, escaped to North Pole and took the guise of Santa. Giving out presents is just a part of his diabolical plan of creating a perfect world for himself and his followers. The elves are actually zombies and vampires Dio created.

Where Rudolf von Stroheim's and Joseph Joestar's prostheses came from
Edward Elric couldn't leave Germany in time after it became a Nazi dictatorship and was forced to assist the SS in making military automail for their war effort. After, he was outfitted with the newest automail technology. After the war, the Americans got hold of the blueprints, automails and Edward Elric himself and he proceeded to make automails for military and civilian use. After Joseph Joestar lost his arm in the fight against Cars, he got himself an automail arm as a replacement.