Mass Hysteria

"But when humans are imagining something out of anxiety or fear, what they imagine remains behind, collects, haunts, and can even take on concrete form. That's how there can be a spider with gorilla legs lurking in the darkness underground, how people can die painting pictures of the Mothman on land, and why Gremlins appear in the air."

- Penelope de la Rosa explains the concept of the Mass Hysteria in JORGE JOESTAR Chapter 14: Desolation Row

Mass Hysteria (集団ヒステリー Shūdan hisuterī) is a strange phenomenal creature that appears throughout the light novel JORGE JOESTAR. It is directly based off of an illness with the same name, and has a similar function.

Description
This phenomenon is based off of an illness of the same name. All sorts of threats and illusions, real or not, are transferred throughout certain populations. This causes fear and rumors, which are later manifested into actual creatures. Hysteria can be fueled by rumors, causing anxiety and fear within people, and eventually causing people to commit suicide because of it. These creatures can be destroyed if people can overcome these fears of them.

Moth (Mothman)
Moth (モスマン Mosuman) is one of the creatures created from people's fears. During the lockdown caused by Alejandro Torres, people were forced to stay in their homes and lock the doors. After that night, the people had feared that another incident like this would happen again. Their fears grew larger in which eventually created Mothman.

One night, the people had spotted Mothman and gathered in La Palma's church, covering the walls with drawings of Moth. They then burn the church down, using the ashes and charcoal to draw more pictures of Mothman. They had all turned into zombies, which kept them alive so they would be able to draw more until the fire kills them again. Since that night, the remaining villagers had began to see Mothman in their homes at night; like Edvard. After that night, all of the villagers had been left filled with fear, only thinking about when they would die.

In the 37th Universe, Moth appears inside the gymnasium of Budogaoka Academy. Where all of the citizens of Morioh had gathered during their emergency. In a trance, the citizens begin to throw gasoline at each other. They are all eventually saved by Koji Hirose with his Blue Thunder. He destroys the gym's walls and breaks the citizens' trance.

Gorilla Spider
The Gorilla Spider (ゴリラスパイダー Gorirasupaidā) is one of the creatures created from the fear of the dark, in a temple in Rome. It appears in a spider-like shape with multiple muscular gorillas fused together. After Lisa Lisa and George search for the Red Stone of Aja, the Gorilla Spider appears and prevents anyone from stealing it. It steals and breaks Lisa Lisa's lamp to prevent her from seeing, increasing her fear. The Gorilla Spider is described to be at least five meters tall, and puts pressure on its victims.

After learning that her fear fuels the Spider, George attempts to make her feel better. At it moves closer from his failed attempt, George explains his feelings and Lisa Lisa kisses him, causing the Gorilla Spider to disappear.

Gremlins (Antonio Torres)
"When people are uneasy, they see things that aren't there, and not just illusions...they make it actually happen. Their fears manifest, and their plane gets damaged just as they imagined."

- Lisa Lisa explains how the pilots' fears manifested into clones of Antonio Torres

Gremlins (グレムリン Guremurin) take the form of Antonio Torres. They were born from the fear when a member of the Royal Flying Corps had spotted Antonio on his plane. This caused rumors to spread, increasing the fear and causing more to be born. They appear as small creatures, that are skinny and have no eyes. The Gremlins were said to have always damaged planes and appeared out of nowhere. Most of the Gremlins are Zombie clones of Antonio, and are described to look like a lizard with no eyes and sharp teeth.