In J&D's ToonWorld, Katz is currently a member of The E.V.I.L Troop.
Katz is a red cat with thin limbs and a long body. He has yellow eyes with small pupils and purple highlights on the lower lids, as well as purple-tipped ears, a purple-tipped nose and three purple stripes across his back. Although he doesn't appear to have eyebrows, sometimes he does, like in "A Night at the Katz Motel". He is a master of disguise and dresses up to match the scam he's planning.
Katz is a smooth and sadistic feline with a British accent, and comes complete with his own sinister background theme music. Like most cats, he has a powerful distaste for dogs, however he reserves a special hatred for Courage. Since his debut in Courage the Cowardly Dog, Katz's top priority has always been helping or advancing his situation in some way. He is competitive, as shown in "Katz Kandy", where he tries to force Muriel to tell him her secret ingredient for her sweet recipes after coming in second place to her in the Nowhere Sweet Stuff Contest for years. Thus, crushing his competition is nothing new to Katz. Katz enjoys a few things, such as making confectionery treats, or managing his collection of spiders. The only things he shows much compassion for outside of his own interest are his "loves" (his spiders).
He is quite the con artist, as well, specializing in scam businesses such as a vacation resort, a confectionery shop, a motel, and a submarine cruise line. It is shown that he often kills his customers; for example, he fed the residents of the Katz Motel to his spiders. Two of his common targets are, of course, Eustace and Muriel (who never seem to remember him from previous cons). Even if Muriel and Eustace are fooled by whatever service he is providing, Courage never falls for his schemes. Because of this, all of his businesses enforce a strict "No Dogs Allowed" policy, which forces Courage to have to sneak in to save his two owners.
Despite his sinister nature, Katz has always enjoyed a bit of pre-defeat "sport" with Courage, which he is quite apt at. The two then engage in small battles in the form of games, such as a handball or a staring contest. It is common in some of these games that Katz will egg his opponent on into losing. For example, during the said staring contest, he kept saying "blink" when he saw Courage's eyes watering. And while he may choose to do things with the least exerted effort on his part when he can afford it, he has shown some slightly above-average athleticism-first shown in A Night at the Katz Motel when he drinks tea and reads while playing racket ball, continued in Klub Katz when he flees wrecking ball Eustace.
- Katz has a distinct theme song that tends to play in the background when he is around.