Fat Cat is a felonious gray Tabby cat and one of the Rescue Rangers' most frequent antagonists. He was introduced as the pet of the nefarious underworld crime lord, Aldrin Klordane. Though Fat Cat presumably respects him, he continues his life as an independent agent and animal world crime boss after Klordane's incarceration. Inordinately proud of his appearance, Fat Cat keeps his whiskers clean. When in the presence of humans, he displays very catlike traits (albeit a tad on the pompous and pampered side), but when with other furries, he wears a purple business suit and has a taste for expensive things. He is a ruthless criminal mastermind, and his plans, though sometimes bizarre, are nevertheless dangerous and sadistic. Fat Cat hates dogs and several of his schemes have been attacks against them. The only thing he hates more than dogs are the Rescue Rangers, which he always tries to get rid of using an elaborate and slow method, rather than killing them immediately. The complexity of his plans usually ends up being his downfall. He has a cousin who lives in Paris.
Fat Cat is usually accompanied by his four henchmen (Wart, Mole, Mepps, and Snout). Despite their combined stupidity, Fat Cat almost always sends them out to do his dirty work for him, as he is too smart or too lazy to dirty his paws himself.
Fat Cat is a recurring threat to law and order as it applies to both humans and domestic animals, and to the Rescue Rangers. Chip, Dale, Gadget Hackwrench, Monterey Jack, and Zipper have outwitted him and his thugs on numerous occasions.
During the original run of Rescue Rangers, Fat Cat made regular appearances at the Disney theme parks. His most notable appearance was in the Disneyland stage show The Disney Afternoon Live!: Plane Crazy, in which he and Don Karnage join forces and steal the X-22 spy plane. As a running gag, Don Karnage continually addresses him as "Cat Fat" by mistake throughout the show. After the initial run of the show and The Disney Afternoon, Fat Cat has not made any appearances at any Disney Parks and is now retired.
- His name may be a pun on the slang term "Fat Cat", meaning a wealthy and powerful person.