The Brain is a genetically enhanced mouse who bears a resemblance to Orson Welles. He is highly intelligent and develops elaborate plans for global domination. His tail is bent, like a staircase, and his head is wide.
Pinky is another genetically modified mouse who shares the same cage at Acme Labs but is substantially less bright. Among his favourite words are "Narf", "Zort" and "Poit". Although also an albino lab mouse like the Brain, he has a straighter tail.
Each week sees Brain come up with a new plan for them to take over the world and every week sees them fail. In common with many other Animaniacs shorts, most episodes are in some way a parody of something else - usually a film.
The catchphrase used in almost every episode is: