Pinky and Brain are genetically enhanced laboratory mice who reside in a cage in the Acme Labs research facility. Brain is self-centered and scheming; Pinky is good-natured but feebleminded. In each episode, Brain devises a new plan to take over the world which ultimately ends in failure: usually due to Pinky's idiocy, the impossibility of Brain's plan, Brain's own arrogance, or just circumstances beyond their control. In common with many other Animaniacs shorts, many episodes are in some way a parody of something else, usually a film or novel.
In the opening credits, Brain is writing a complex formula about the Universe Explained (simplified) and the resulting answer is THX 1138 (1971) - the title of the first film by George Lucas.