He has an alternate version of himself in an opposite universe called The Dog. Among his other alter egos is the 'Duke of Dork', Duane Dibbley, who represents the 'nerd' stereotype and the Cat's idea of a meaningless existence. In the episode Demons and Angels, The Cat's good and bad side are seen, his good side being a "Ned Flanders" religious type residing in a hooded robe and sandals, whilst explaining to the normal cat that he is his higher self, his spiritual side, extrapolated from his being the normal cat replies "Extrapa"what"elated, buddy there is no way you are a part of me, no part of me would ever be seen alive in sandals". This version is eventually shot at and blown up with the "divine" Kryten when they believe that a bomb thrown from the "Low" versions of the crew is a greetings gift. The other half is more savage and gangster-like than either of the other cats, notably he has no fashion sense being nearly dressed in nothing but rags, furs and black leather.His teeth have grown way out of proportion making him more like a "Sabre-toothed cat", this version was destroyed when the two new Red Dwarfs regenerate into the old one. An alternative Cat is briefly encountered when the Dwarfers meet themselves from an alternative timeline and are joined by Kristine Kochanski. This Cat seems far more upper-class and subdued in appearance, in line with Kochanski's nature. Cat's mirror opposite is also encountered in the mirror universe (Series VIII episode "Only the Good..."), a wise professor who finds it ridiculously easy to pronounce profoundly long words, e.g., Caesiumfrankolithicmixialubidiumrixidixidexidoxidroxide. This version of The Cat is more intelligent than both the original Cat and Duane Dibbley> In 'Ace' Rimmer's universe (series IV episode "Dimension Jump) is the base priest. this Cat smokes a pipe and congratulates Ace Rimmer on helping a sick boy recover.
In early episodes, The Cat exhibits typical feline behaviours such as licking anyone who gives him food, playing with 'shiny things' and marking his territory, for which purpose he carries a small spray-can, of which the contents are unknown, in his pocket. While scent-marking, he repeats, "This is mine, this is mine, and all of this is mine." The Cat also had shown little concern for the welfare of his crewmates. His extreme self-confidence results in him thinking himself to be irresistible to women, without ever having met any. He is originally very self-centered, acting purely without concern when his old mentor the "Cat Priest" dies, giving Kryten an earring which he hates on the day before his automatic self-destruct and choosing to finish his lunch rather than carry Lister to the medical bay when he collapses, he later improves however. In the episode Stasis Leak, the crew discover a portal, referred to as a "Magic door" by Cat, which allows them to go back before the crew are wiped out, he sees actual human females, and remarks "They make me want to do something. I don't know what it is! Whatever it is, I wanna do it a lot of it!" By Series IV, the Cat becomes less obsessed with mating, and begins to develop a friendship with Lister — possibly due to their mutual contempt for Rimmer. The Cat vaguely taught Lister the meaning of the cat word JOZXYQK, which is a sound that is made when one's sexual organs are trapped in something, during a game of Scrabble.
As he learns to relate to the crew, he eventually stops licking them and marking his territory, and even begins to show genuine concern for others on several occasions. He becomes a skilled pilot of Starbug and develops an ability to "smell" danger, even in space — although he does not grasp scientific terms, describing anomalies as either "wibbly thing" or "swirly thing". Also, when a complicated issue arises or a strange anomaly is encountered, he is commonly known to pose the question, "What is it?", usually until the various explanations he is given make sense to him. His escape plans are almost always fashioned out of fantasy, and are generally reliant on objects that the crew either do not possess or are nonexistent anyway for success. For example, he suggested that they "drop the defensive shields" when they had none, and in another situation, to don their "rocket pants", which Kryten promptly pointed out they didn't have and hadn't even been invented. Kryten usually replies to these types of suggestions by saying "it is an excellent plan sir with just two minor drawbacks: one, we don't have any (whatever the cat said), and two (something related to what the cat said - for instance, there's no such thing as rocket pants)". When the crew finally does go with one of his plans, the Cat questions their sanity for heeding his own advice, remarking, "What if we all get killed? I'll never hear the last of it!".
He takes particular pleasure in using the food synthesizer to get fish dinners, at one point standing in front of it repeating the word "fish" six times as the machine cranks out meal after meal, much to his obvious delight.
In the episode "Parallel Universe", The Cat performs the song "Tongue Tied", which appears as a dream sequence on a "dream monitor". The song was later released as a single in 1993, and reached number 17 in the UK charts. The artist was listed simply as "The Cat".
In the first and second pilot episodes of an American version of the television series, the Cat was played by Hinton Battle and Terry Farrell respectively. (Farrell's version was more outwardly catlike in appearance.)