One of the most recognizable elements of the Jojo's Bizarre Adventure series are the Stand abilities wielded by the characters, which take the form of humanoid spirits that provide their masters with incredible powers. Yet, these iconic abilities only came about because series creator Hirohiko Araki had a very particular bone to pick with the traditional portrayal of paranormal abilities.
In Jojo, Stands are the manifestation of their users' soul and fighting spirit. Although some Stands can think, speak, and act independently of their masters, every Stand is actually a part of its user, and damage suffered by a Stand is immediately passed on to its user. Stand users don't have to be human, and several animals, from chimps to rats to turtles have been shown to possess them. Stands also come in a variety of different types, like humanoid or non-humanoid, or natural or artificial. Stands can also have either short or long-range effects, but the types of powers Stands wield in Jojo are almost unlimited.
Stands were first created in Stardust Crusaders, the third part of Jojo. Joseph Joestar first explains Stands as "apparitions created by [one's] own life energy" and that they gained the name because they "stand beside you." Out of universe, however, the story is a bit different. In an interview in Jojo6251 magazine from December 1993, Araki says he wanted to create a new type of ability and had people around him suggest implementing a type of ESP or psychic power for his characters. Araki, however, didn't like the idea of being able to move things via willpower or mental ability alone, and instead preferred a more logical explanation for how an object could be manipulated in that way. A ghostly humanoid figure moving an objective physically, which was invisible to those without Stands, offered a far better explanation in his eyes. Amusingly, the name Stand came not from the fact that these figures "stand" alongside you, but because they loomed like a "light stand," as in a tall lamp, nearby.
What if Stands Hadn't Been Created?
In Jojo, most Stand abilities could function without a humanoid figure attached to them. Some, such as Hol Horse's Emperor or Joseph's Hermit Purple aren't traditionally depicted with a humanoid form (though they supposedly still possess one). Still, even these abilities manifest physically. In the case of Emperor and Hermit Purple, they appear as a gun and as thorny vines, respectively. As manifestations of a character's soul, Stands actually pull double duty by providing some insight into their masters. The nature of someone's Stand ability and the design of their Stand are often reflective of their personality, so they offer a new route for some characterization. For example, Koichi Hirose's Stand Reverb changes as the story progresses to reflect his character growth--something that would be harder to do if he just had the Reverb power directly rather than seeing it as a separate manifestation.
It's not hard to imagine Jojo's Bizarre Adventure characters using psychic powers instead of Stands to accomplish the same things, but a lot of the charm of Jojo would certainly be lost in the process. Simply by thinking outside the box a bit, Araki managed to come up with Jojo's Bizarre Adventures' single most recognizable trait, defining his series as a classic that stands the test of time over 30 years later.
Source: Jojo6251