Brain is a mouse that was genetically enhanced, along with Pinky in Acme Labs research facility. He is the more "evil" of the duo and plans to take over the world in every episode, which usually ends in failure. Ultimately, he sees himself as doing the world a favour by trying to control it, when really he's a bit of a megalomaniac.
Brain first appeared, alongside his counterpart Pinky, in the show Animaniacs in 1993. The pair soon gained their own show in 1995 called Steven Spielberg Presents: Pinky and the Brain, produced by Spielberg and Warner Bros. Finally, they appeared in a last series known as Steven Spielberg Presents: Pinky, Elmyra and the Brain which was not as successful as their previous shows.
Brain's character was based on Tom Minton, a colleague of the producer Tom Ruegger. Ruegger said he had wondered what it would be like if Minton and Eddie Fitzgerald (The inspiration for Pinky) attempted to take over the world and there began the idea for Pinky and the Brain.