Robert E. O. Speedwagon is a major ally featured in Phantom Blood and Battle Tendency.
Formerly a Londoner thug residing in Ogre Street, Speedwagon befriends Jonathan Joestar and, despite remaining a powerless human, becomes a loyal ally to the Joestar Family during his whole life and beyond thanks to the company he's founded: the Speedwagon Foundation. His company supports the Joestars in Stardust Crusaders, Diamond is Unbreakable, and Stone Ocean.
Robert E. O. Speedwagon is a man who lived in darkness ever since he was born. Growing up on the dangerous Ogre Street, he stole things to live and met all kinds of horrible people in his life. It reached the point of him being able to tell a good person apart from a bad person just by their smell. He eventually became the leader of the thieves in Ogre Street and befriended a Kempo Master and Tattoo.
During his youth, Speedwagon had traveled the world, experimenting with various exotic animals in Africa, strange Asian plants and Caribbean tornadoes.
Speedwagon first appears as an Ogre Street thug boss expecting easy pickings from Jonathan Joestar when he entered the street in search of the antidote to the poison that Dio Brando gave to his father. But finding himself outmatched, Speedwagon realized Jonathan spared his men and ordered the others to stand down, offering his services in leading Jonathan to Wang Chan. Fearing for Jonathan's safety, Speedwagon then accompanied him to the Joestar Mansion where he saw through Dio's attempt to lull Jonathan's guard with feigned remorse. When George died protecting his son from being stabbed by Dio, Speedwagon voiced his utmost respect to the Joestar family. Following Jonathan's battle against a newly vampirized Dio, Speedwagon takes Jonathan to the hospital where the youth was cared for by his childhood friend Erina Pendleton.
Speedwagon accompanies Jonathan and Ripple master Will Anthonio Zeppeli to Windknight's Lot in their mission to finish Dio off, though Zeppeli mentions that Speedwagon could never master the art of the Ripple, a fact that greatly distressed Speedwagon. Upon arriving at Windknight's, Zeppeli attempts to push a pressure point in Speedwagon's midsection anyway, in order to give him the ability to harness "small ripples," but missed the right location and ended up hurting Speedwagon instead. The group encounters Dio soon after and is forced to fight off an army of zombies; Speedwagon aids by attacking a few with a sledgehammer. When Zeppeli's arm is frozen by Dio, Speedwagon thaws it by placing it on his own flesh. After Zeppeli's death at the hands of Tarkus, he takes on wearing his hat as a remembrance of their fallen ally.
In the climactic battle against Dio, Speedwagon assists the group by fending off zombies and making an attempt to hinder Dio by destroying his arm. Following the battle, Speedwagon smashes the Stone Mask with his sledgehammer. The morning after Jonathan and Erina marry, Speedwagon is seen reading about their story in the newspaper, only to rush to the docks after realizing their honeymoon cruise was about to set sail. He successfully sees them off, though did not know of the immediate tragedy that would befall them until later.
In the years following the death of Jonathan Joestar, Speedwagon had traveled to America, where he discovered oil and formed the powerful Speedwagon Foundation. It is also during this time that he became an uncle figure to Joseph Joestar, noting him as a dead-ringer of Jonathan despite their opposing personalities. At some point, Speedwagon was kidnapped on a hijacked plane and was going to be sold for ransom, if not for the efforts of Joseph.
Immediately before the events of Battle Tendency, Speedwagon learns of the discovery of a human-like figure embedded in a pillar holding numerous Stone Masks.
Speedwagon, now an old man, and his team meets with Straizo in order to show him the inactive Pillar Man so that he may use the Ripple to destroy him. Unexpectedly, Straizo betrays Speedwagon and mortally wounds him while killing off the others to use their blood to become a vampire. Speedwagon is then dumped into the river by Straizo to prevent the pillar man from absorbing his blood and is eventually 'rescued' by the Nazi major Rudol von Stroheim, who took the pillar man for research. Speedwagon seems helpless in the presence of Stroheim while pleading for him to not revive the being that the Nazi named Santana. But when Santana breaks out of his containment and kills most of the German unit, Speedwagon was saved by Joseph. After Santana's defeat and containment, Speedwagon travels with Joseph to Italy in order to meet Caesar Anthonio Zeppeli, where he disappointingly watches as the two squabble in stark contrast to the cooperation of Jonathan and Will.
He goes with them to where the three other Pillar Men are, and bears witness to the awakening of Wamuu, Esidisi, and Kars, becoming a bystander in the ensuing fight. Afterwards, Speedwagon spends most of the story accompanying Erina and Smokey, while withholding information about the Pillar Men and Joseph's life-threatening predicament from Erina at his request.
Speedwagon and Smokey reappear once again during Joseph's battle with Kars, having come with assistance from the Nazis against the army of vampires. Once again, Speedwagon becomes a spectator to unfortunate events while explaining to a concerned Smokey that they must respect the wishes of Erina and Lisa Lisa to not reveal the latter's identity to Joseph. When Kars successfully turns into the Ultimate Lifeform and proceeds to hunt down Joseph, Speedwagon desperately begs for Joseph to go into hiding rather than attempt to face the Pillar Man head-on as he didn't "want to lose him too", but is ignored as the young man goes off on his own.
Later, Speedwagon is one of the group of people who attends Joseph's funeral, comforting Erina as he is the only other living person to grasp the scope of her agony and the tragedy of the Joestar family. However, Joseph himself immediately shows up and reveals his surviving the final confrontation with Kars, much to everyone's joy and relief.
Speedwagon dies in 1952 of a heart attack at the age of 89. As a lifelong bachelor, he leaves no family behind. After his death, the Speedwagon Foundation is dedicated to biochemical science and technology, and assists the Joestar Family throughout Parts 3-6. His men go on to create a new prosthetic hand for Joseph, help Jotaro destroy the remains of DIO as well as study the Stand-creating Arrow, analyze Giorno Giovanna's Joestar bloodline, and maintain Jotaro's health after his Stand and memory discs are stolen by Whitesnake.
In the Legacy of Chris Thorndyke,
And he is reprised by Keith Silverstein in the English dub and Yoji Ueda in the Japanese dub.