The Brain

"Pinky: Gee Brain, what do you want to do tonight? Brain: The same thing we do every night, Pinky: Try to take over the world!"

- The Brain to Pinky almost every episode (also their most famous lines.) "Pinky, are you pondering what I'm pondering?"

- The Brain asking Pinky if they are thinking the same thing (only to always get an idiotic response).

The Brain is the main protagonist villain of the Pinky and the Brain shorts from Animaniacs, as well as its spinoff Pinky and the Brain and Pinky, Elmyra and the Brain.

The Brain is a lab-mouse who (upon being mutated in an experiment) gained superhuman intelligence and desired to take over the world in order to make it a better place. However, despite his numerous claims of success, Brain never ends up succeeding at his end goals, both due to his idiotic partner Pinky and, in some ways, himself.

He was voiced by Maurice LaMarche, who also played Lrrr in Futurama, Father in Codename: Kids Next Door, Mr. Big in Disney's Zootopia, and sometimes Yosemite Sam in Looney Tunes.

Story
Both Brain and Pinky are laboratory mice who underwent an experiment to make them rational. The experiment had different results on each of them, turning Brain into a super genius, while Pinky also becomes sentient but incredibly stupid. Brain then decided he would use his superior knowledge to take over the world and make it a better place using his intellect. He convinced Pinky to aid him in his plans, and the two of them try a new plan to achieve world domination every night.

Personality
Brain is a manipulative genius with a calm and overconfident personality. He almost never loses his cool, even when Pinky commits stupid errors that mess his plans completely (though he does often display clear annoyance). He also seems to be egocentric and arrogant. Despite his desire to conquer the world, he truly believes that by doing so he can make it a better place, will never resort to murder to accomplish his goals and deep down he does care about Pinky.

There are also some world domination plans even he won't attempt as they are sick even for him: for instance, he was unwilling to use a plan involving selling cigarettes to children. Brain's good intentions are highlighted with his rival called Snowball, a hamster who also planned to conquer the world, but who is far more evil and cruel. Brain is disgusted by Snowball's methods and will stop at nothing to prevent him from taking over the world.

Trivia

 * Brain's voice and character was largely inspired by famous actor/director Orson Welles, whom his voice actor, Maurice LaMarche, would often listen to while warming up. In fact, the Animaniacs short "Yes, Always", in which Brain and Pinky were hired to provide voice work for an episode of Animaniacs, was a direct parody of an infamous audio recording in which Welles heavily criticized the mediocre writing and directing of several commercials he was to voice over, with Brain quoting his complaints word for word.
 * Only one of Brain's plans succeeded. He used time travel to provide Fire to Mousekind before Mankind could discover it.
 * The reasoning is that Fire is the First One advantage Man had which placed them at the top of the Food Chain. Upon returning to the "present", Mousekind was indeed the dominant species on the planet. The drawback was each and everyone they saw were just like Pinky, right down to the "Narf!" catchphrase, forcing Brain to remove the changes he made to history, as, although he could rule the world, he did not want to.