Parallel Worlds (並行世界 Heikō Sekai), also referred to as Worlds Next Door (隣りの世界 Tonari no Sekai), Other Dimensions (異次元 Ijigen), or Alternate Universes, are physical dimensions that co-exist and operate independently of each other. The existence of such worlds plays a major role in Steel Ball Run as the basis behind Funny Valentine's Stand, Dirty Deeds Done Dirt Cheap.
- Main article: Dirty Deeds Done Dirt Cheap
In Steel Ball Run, an uncountable number of parallel worlds are assumed, each following the same basic chain of events. In one of these worlds, referred to as the "base world" (基本世界 Kihon Sekai), a certain Saint's Corpse is scattered across the United States, leading to a horse race almost two millennia later with the secret aim of collecting the corpse. The same horse race occurs in other parallel worlds, but other goals take the place of the corpse, such as diamonds held by President Funny Valentine.
Funny Valentine's Stand, Dirty Deeds Done Dirt Cheap, allows parallel worlds to overlap with each other, permitting people and objects to travel between them by preserving their internal gravity. In order to do so, Valentine must compress the target between any two objects, which can range from doors and drawers to spilled water. However, with the exception of Valentine himself, only one instance of any person or thing can exist in any parallel world; if two or more exist, they will slowly be drawn toward each other until they collide and are both erased. Though Valentine is ultimately defeated by Tusk ACT4's infinite rotation, which affects Valentine's gravity itself, he manages to summon a Parallel World Diego to the base world in a final desperate bid to secure the corpse for America's gain.
Within JORGE JOESTAR, various iterations of Funny Valentine and his grandson, The Funniest Valentine, possess versions of D4C. However, the two of them have access to a different set of parallel worlds. In Funny's case, though none of his parallel selves wield D4C, The Funniest's parallel selves do; for The Funniest, whose primary iteration in the novel comes from a different universe than Funny's, it is the other way around. Thus, Funny can collect several versions of The Funniest with D4C from his parallel worlds, whereas The Funniest can collect multiple versions of Funny with D4C instead. However, iterations of Funny and The Funniest with D4C are not protected from their alternate selves, and can be annihilated if they come into contact with them.
In Eyes of Heaven, a version of DIO in a parallel world fully evolves his Stand into The World Over Heaven, using it to triumph over Jotaro Kujo and rewrite the universe to his liking. Funny Valentine stumbles across this version of DIO while attempting to escape the effects of Tusk ACT4, leading DIO to discover the existence of multiple worlds. DIO thus sets out to conquer the base world and obtain the Saint's Corpse, overwriting various characters to turn them into his subordinates.
The mouth of Vanilla Ice's Stand, Cream, serves as a portal to an "endless dimension of darkness" that even its user cannot perceive. By devouring both its user and itself, Cream is able to enter that dimension itself, leaving a void wherever it travels that erases everything it comes in contact with. Okuyasu Nijimura's The Hand functions similarly, erasing whatever its right hand touches, but where the objects it erases are sent to is a mystery even to Okuyasu.
Yoshihiro Kira possesses the ability to create a pocket dimension within any photograph taken by his camera. Any action taken within the photograph is reflected in the real world. In addition, the space depicted in the photograph is sealed off from the real world: those attempting to enter will find themselves on the other side, while those inside cannot escape. By trapping himself inside his photographs, Yoshihiro is able to live on after his death as a ghost.
Illuso's Stand, Man in the Mirror, allows him to create another world visible through reflective surfaces, through which he can freely transport any part of himself or anyone else. Man in the Mirror’s world is not a physical world, but a dimension created by spiritual energy; as such, only the spiritual forms of victims pulled into the mirror dimension appear inside it, and those within are returned to the real world upon Illuso's death.
After awakening Made in Heaven, Enrico Pucci uses its ability to accelerate time for all living beings, allowing the survivors of the ensuing chaos to cross over into the next cycle of the same universe. During this time, living beings experience everything that will happen in the future as it passes, and these experiences are engraved into their souls; as such, they will experience premonitions of future events before they happen, a phenomenon which Pucci hopes will lead them to happiness. Those who do not survive the transition are replaced by similar counterparts in appearance and personality, who play the same roles in fate.
The hooks and cables inside Pork Pie Hat Kid's mouth are said to be able to travel through another dimension when Pork Pie Hat Kid sends them into a bowl of water. The hooks then reappear from that dimension through the bottom of any desired object, such as a bird's feather or a beetle.