Fatso is Kakoo's pet cat. It is unknown if Fatso is a boy or a girl. He is only mentioned in An Oobi Christmas, where (s)he is heard meowing while Kakoo is trying to lie to Oobi about having a cat. It is presumed Fatso has a terrible life, because Kakoo tends to play rough with animals. It is unknown what he or she looks like.
Fatso is mentioned and heard in An Oobi Christmas.