In a Reddit conversation about fan theories, one “Monsters, Inc.” viewers had a puzzling idea of how the city of Monstropolis was powered before they used the screams of children. U/curly indicates that the advertisement for “Monsters Inc.” in the film prides itself on using “clean” energy, a concept used in the real world. In fact, sources like coal and crude oil are considered “dirty” energy sources because they are non-renewable and destroy the environment. A source like natural gas is considered “cleaner” due to its less impact on the environment, but it’s still not the best. Meanwhile, by all accounts, sources like solar or wind are “clean” energy, as they cause the least amount of damage.
In “Monsters, Inc.”, the screams of children are equivalent to natural gas because “it’s cleaner, but still not as loud,” explains the original poster. Switching to children’s laughter would be the cleanest, like solar energy, as harvesting methods do not cause harmful effects, such as injuring children. So it’s been suggested that the “dirty” energy, used before the movie’s timeline, is the blood of children. The Reddit user explained: “Something dirtier and literally non-reproducible that the monsters have left as a society.”
It’s a pretty dark theory that the movie is geared towards children. However, when analysis “Monsters, Inc.” from an adult lens, logic makes sense.
https://www.looper.com/749297/the-tragic-monsters-inc-fan-theory-thats-lighting-up-reddit/ The Tragic Monsters, Inc. Fan theory lit on Reddit