The advancement and sophistication of the monster world in Monster Inc is evident. They are clearly living in a more technologically advanced era than we are. They are skilled in inter-dimensional travel and their means of energy is the resonance of a child’s scream or laughter.
A theory suggesting that the giants are petrified of the Black Plague has been much debated over. Let us see if this is just another speculation or it holds any weight at all. The following evidence will help us understand the grounds of the theory.
Almost a century ago the monsters tested their technology to open an inter-dimensional portal. Although it was a simple gateway connected to a nuclear power plant that opened the door to a different realm, they did succeed. The first-ever monster to arrive was the big hairy monster. He steps into the portal and enters into the room of an ill child.
The child is terrified at the sight of the monster and starts yelling. Well so does the monster who then quickly retreats from the door back to his own space. In that scene, we can see the child’s scream messing with the monster technology. There is an unexplained surge of power. And in that very moment, there is a noticeable resonance between the power source and the sonic vibrations.
The second indication comes from the flea carrying Yersinia Pestis. At the time when the first monster pulled inter-dimensional travel, he was not checked for any potential dangers or contaminants that he might have brought back with him. Obviously they are aware of fleas and their potential.
Later in the day, the monster goes home, back to his family along with the flea he just transported into his realm. The flea may easily find a corner to breed and start his own family. The monster paid no heeds to that itch on his shoulder. And thus unleashed the terror of a germ that caused his neighbors to show signs of illness. That was the beginning of a pandemic in the monster world, the roots of which are attributed to be the Black Plague that he acquired from the sick child in the human world.