|“||Monkeys, apes, they all hold stuff with their feet, man! We're talking freaks of nature!||„|
|~ Ron Stoppable|
|“||There once was a man who's prison was a chair. The man had a monkey, they made the strangest pair. The man was the prisoner, the monkey held the key. No matter how he tried, the man couldn't flee. Locked in his prison, terrified and frail. The monkey gaining power, keeping him in jail. The man tried to keep the monkey from his brain, but every move he made, he made the monkey's game. The monkey ruled the man, it climbed inside his head. And now as fate would have it, one of them is dead.||„|
|~ Narrator for a commercial for Monkey Shines|
Maniac Monkeys is TV-Tropes-popularized term which involving non-human primates which are apes and monkeys in general portrayed in negative light, especially the ones that possesses more anthropomorphic traits than their kinds would.
Everybody knows that monkeys and apes are related to human species due to all of them are classified as primate and also capable in emotions like humans would. In some fictions, some monkeys and apes portrayed with greater awareness where they began to see humanity as rival for their race due to some similarities that they had.
Though highly intelligent non-human primates and mankind can live coexist peacefully, not all of these non-human primates are good. Some of them even go bad like humans would, and if they rally their fellow non-human primates against humanity, the result would be catastrophic: Human species can either perished or enslaved or worse, these non-human primated can wind up to destroyed all life on Earth and if they were lucky, they can move to another planet to drain the said planet's resources.
Fortunately, there are still those whom can oppose them and prevent the worst from happening.
Just like other villains in general, how they came into being were varies, ranging from freak scientific/sorcerous accident, mistreatment by human species, or unexpected course of evolution.