Robert Speedwagon

Summary
Robert Speedwagon was a gangster who became an ally to Johnathan Joestar. He assisted Jojo with many cross examinations and investigations. He was quite popular with the ladies, as he nearly steals Erina from JoJo. Eventually he met his fate in the secret chamber under the Joestar Manor, where he jumped in front of a sword from a zombie in order to save his friend. Unfortunetly for Speedwagon, he was revived as a zombie by DIO and turned into a slave, forcing him to hold Erina hostage. During the ensuing battle, he attempts to kill JoJo multiple times. In the end, he was buried with DIO under the Joestar Manor and unlike DIO, did not survive. When DIO returns in part 3, he uses the decapitated body of Speedwagon as his vessel.

Pre-Phantom Turnabout
Not much is known about Speedwagon before the events in Phantom Turnabout, other than he was born in 1863 and was a gangster, though it's safe to assume he fought Johnathan and was impressed due to JoJo's valor and mercy, much like his JJBA counterpart. Instead of ambushing Dio Brando at the Joestar Manor, as was the case in JJBA, somehow they arrived too late. The reason for why they were late is unknown.

Meeting Zepelli and Straizo
Speedwagon arrived at the Joestar Manor with Jojo only to find that not only were they too late to save George Joestar, Johnathan's father, but Johnathan was accused of killing his own father. When they first Met William Zepelli, Speedwagon was just as anxious for answers as was jojo, but was less trustworthy of the man. While they questioned Zepelli, Speedwagon picked up on the fact that Zepelli was working with multiple people, which made Speedwagon trust him even less. During the questioning, Speedwagon grew very heated due to Zepelli's reluctance to give the pair any information and needed to be calmed down by JoJo.

When JoJo asks Zepelli why he is helping them, Zepelli calls over his pupils, Straizo and Dire to test the pair of heroes on their wits to not only see if they are innocent, but trustworthy as well. During their debate, Speedwagon points out that JoJo and himself were both gone when the murder occurred, but Straizo simply offered a possibility that JoJo had committed the murder and was simply there with Speedwagon to tamper with the scene. This quick rebuttal shocked both men initially. During the debate, Johnathan was temporarily taken away to be questioned by the police, and Speedwagon took over the pair's investigation. The debate came to a close when Speedwagon shows that the gun has a missing bullet, and until it is found, it's impossible to determine a culprit. Not only this, but he also deduces that the only possible location the bullet could be is inside the killer, due to the lack of gunshot holes in the walls surrounding the crime scene and the body. After this, Straizo tells Speedwagon that the "medecine" that was supposed to be curing George Joestar was actually killing him. At this point Johnathan returns from questioning, and takes over the investigation again. After finally proving their worth, the pair are finally told about the stone mask and Hamon.

Encounter with Erina
For most of the encounter, Speedwagon stays away, completely aware that he would just be a thrid wheel in their relationship. Eventually, he does get involved when Johnathan inevitably attempts to flirt with Erina, but it completely backfires, as Erina nearly falls head over heels for Speedwagon instead (as he rolled higher than Johnathan).Speedwagon redirects her attention back to Johnathan though, and joins the conversation. During said conversation, he learns about Dio Brando, the former location of the Stone Mask, and the bullet casing found in JoJo's room.

Battle Under the Joestar Manor and Death
JoJo, Zepelli and Speedwagon find a secret passage leading to an underground chamber hidden in Dio Brando's room. Upon arriving in the chamber, they encounter an army of zombies, all created by Dio. Even though he is not instructed in the ways of hamon, Speedwagon still takes down several zombies. Then, the group find a powerful zombie, that Speedwagon and JoJo eventually defeat together. As it dies, the zombie attempts to stab JoJo with it's sword, but Speedwagon jumps in the way, saving JoJo, but suffering a mortal wound in the process, which kills him a few minutes later.

"Resurrection"
After a little while, he is resurrected by Dio as a zombie and is forced to do his bidding. He is instructed to guard Erina, whom Dio has taken hostage. Eventually, Dio loses his logic chess against Johnathan, when Dio Brando reveals himself to have been DIO all along. Just then, a massive battle erupts between JoJo and his allies vs DIO and his army of zombies (including Speedwagon). Speedwagon directly tries to kill Johnathan multiple times during the battle, though showing some restraint, much to the dismay of DIO. Eventually, Zepelli sacrifices himself in order to bury DIO and his army. Though DIO succeeds in killing Zepelli, it's far too late, as the entire chamber collapsed on the army, burying DIO alive, and killing Speedwagon (again), along with the rest of DIO's zombie army.

Legacy
Although Speedwagon passed under the influence of DIO, he was still properly remembered for his heroisim before the enslavement, as Straizo and Dire created "The Speedwagon Foundation" to honor the gangster's memory. This organisation would affect all of the following JoJo cases. Unfortunately for Speedwagon, DIO eventually stole his decapitated body in order to use against Jotaro Kujo in his quest to destroy the Joestars in Stardust Turnabout. Sometime before his death, he had a child, and the Speedwagon dynasty will soon intersect with the Joestars once more.

Personality and traits
His most distinguishable quality was his undying loyalty to Johnathan Joestar. This was due to his immense respect for JoJo's chivalrous ways. Speedwagon detests spoiled, stuck up, rich men, which is what sparks his distrust for Dio Brando. Speedwagon also has a lot of unexpected wit, which is demonstrated when he identified that there were other people while talking to Zepelli for the first time as well as when he determined the location of the bullet while talking to Straizo. He will use this to his advantage when he can to catch people off-guard. One of Speedwagon's flaws is his defensiveness. It is very hard for him to trust people, and will take a very long time, which ironically contrasts Jojo's trusting nature

Johnathan Joestar
As mentioned before, he deeply respects Johnathan. During their time together, Speedwagon often acted as more of support in combat unlike Zepelli, who was more of an equal. Even though he lacked the combat strength, JoJo still treated him as an equal, which strengthened their relationship even more. Even out of combat, he supported JoJo emotionally and relationship-wise, being a wingman for JoJo when Erina momentarily lost interest in him.

William Zepelli
Although he didn't trust Zepelli at first due to the secretiveness of Zepelli's work, over time he eventually grew to trust him more and more. Although he wasn't nearly as close as Johnathan was to him, he still was friendly to the end.

Straizo
The relationtionship here is very similar to Zepelli's in basic style, but very different in the actual detail of it. For example, Speedwagon grew more friendly over time simply because he began to trust him over time. On the other hand, Speedwagon's relationship with Straizo was forged almost instantly when they met after Speedwagon passed the test of wit. After that, they gained respect for each other. Even though they weren't "friends" per say, they still respected each other enough that Strazio would found the Speedwagon foundation in Speedwagon's name.

Dio Brando / DIO
Speedwagon got a bad feeling about Dio as soon as he layed eyes on him. His anit-trusting nature certainly didn't help soothe things out. He started to distrust and despise Dio the more he learned about him, but never got the chance to act on his feelings as he was killed before meeting him again. After Dio resurrected him, the part of Speedwagon's mind that was left untainted grew it's hate of Dio to an unspeakable level, as he was forced to attack his best friend and Erina.

Powers and Ablilities
Although he could night fight with Hamon, he was still useful in battle. He fought using a gangster fighting style. He also had a knife on him at all times, which he seemed rather obsessed with. His weapon of choice has a top hat equipped with blades. The hat was most useful when it was thrown, and it could channel Hamon due to it's metal blades, making it an effective weapon against zombies, and especially vampires when paired with a Hamon user.