Fat Bob is a relative of Eric Cartman in some way. His relation to the Cartman family is unknown. He made his first appearance in the episode "Merry Christmas Charlie Manson!", and appeared again at Mabel Cartman's funeral in the episode "Cartmanland".
He is overweight like most of his family and he wears a pale green t-shirt which reveals the top of his chest hair and a pair of brown trousers and black shoes.