Brain, an orange cat with a purple T-shirt with a black line, appears as a common assistant to Top Cat. Contrary to his name (which appears to have been given in jest or sarcasm), Brain is the dimmest-witted member of the alley gang, and is notorious for being unable to keep a secret. He is also portrayed as stuttering. He also seems to be in charge of the group's money (which they rarely have), and he runs up and down the road. Despite his apparent stupidity, he can sometimes say something brilliant, which T.C. instantly rephrases to make it sound like T.C. thought of it himself. He is voiced by Leo De Lyon in the TV series.
In the movie, his voice, by Jason Harris, is a little deeper, and he is made even more obviously stupid.