Cats are stereotypically stealthy, quick, graceful, and acrobatic. Ninja are stereotypically stealthy, quick, graceful, and acrobatic. So of course, in a work involving both cats (whether as literal Talking Animals, merely symbolic Animal Motifs, or something in between) and ninja themes, you should expect the ninja role to tend towards cats.
Cats in general have a reputation for being an adorable pet, as well as for being self-reliant, hunting down mice with either ruthless efficiency or sadistic pleasure, having nine lives, and trying to sneak around everywhere. Ninja are renowned for being masters of stealth, difficult to kill, and ruthlessly efficient or sadistically deadly assassins. Naturally, some works of fiction ignore the fact that cats tend to knock over household items and prefer to exaggerate their "stealthy" tendencies by turning felines into ninja.
Typically expect characters of this nature to be either Badass Adorable or Tall, Dark, and Handsome (if not some version of Evil Is Sexy). They may be an example of Cats Are Superior, if they're portrayed as arrogant, or Cats Are Mean, if they're antagonists.
These cats often have all-black fur due to ninjas being generally portrayed as wearing all-black outfits.
This need not apply solely to household cats; it is possible for some species of big cat, such as tigers or panthers, to be portrayed as ninjas - big cats are less common with Talking Animals, thanks to Rule of Cute, but may be more common with Animal Motifs, due to Rule of Cool.
Not related to With Catlike Tread or to Classy Cat-Burglar. See also Cats Are Superior, Cats Are Mean, Animal Stereotypes (generally the cause of ninja cats), and Good Animals, Evil Animals (when the cat ninjas are evil, often when they're black or Siamese). See also Female Feline, Male Mutt (in cases of overlap, you can usually expect a cat ninja and a dog bruiser).
- Obi of Akagami no Shirayukihime has a cat motif and is unquestionably a ninja even if he's never outright called such in the European based fantasy setting seeing as he is a Stealth Expert kunai user who likes to keep his face covered and was formerly an assassin for hire.
- From Bleach, Yoruichi was once head of the Onmitsukido (the ninja branch of the Soul Society) and can transform into a cat.
- Played straight in Samurai Pizza Cats, where all of the protagonists are cats.
- In Buck Godot: Zap Gun for Hire, the Human Delegation's security staff includes a talking cat named Martin who specialises in sneaking and stealth, and dons a full-on McNinja outfit when things get serious.
- Usagi Yojimbo has three ninja clans each consisting of one animal. One of these clans is the Neko Ninja.
- Blood and Revolution has Saitou assigning animal motifs to most of the characters; Aoshi - a literal ninja, last head of the Oniwabanshuu - is given a panther (made only worse once Aoshi becomes a vampire and developes cat eyes). To Aoshi's annoyance, he eventually evolves into a chaos demon, and because Your Mind Makes It Real his natural form does have a cat tail.
- In the Petvengers fancomics, secret agents and assassins are usually depicted as chubby little cat people.
- In the Discworld novel, The Amazing Maurice and His Educated Rodents, the titular cat, Maurice, is trapped in a dank underground cellar, pursued by massive killer rats operating under the eldritch direction of the evil Rat king. Maurice, a cat given human-level intelligence after a magical accident, has to pull off feats of Ninja-like combat to fight his way out and escape: these involve swimming through mud and sewage and wriggling through increasingly smaller spaces.
- The Legendary Starfy gives us Shurikit and Kittana, two rival cats who are constantly practicing their ninja skills against each other. Shurikit also teaches Starfy a few abilities.
- The Elder Scrolls
- Throughout the series and in background lore, the Khajiit, a Cat Folk race, are naturally inclined toward stealth, and can often be found as assassins, spies, and thieves in other provinces.
- In Skyrim, some of the Dark Brotherhood members that attempt to kill you are Khajiit, although none are in the core (joinable) group. The Thalmor are also not above hiring Khajiit as assassins and spies, such as the one that stalks you in Riften and another that is hired to kill Malborn. If the Dragonborn is a Khajiit, they naturally get a +5 bonus to Archery, Lockpicking, One-Handed, Pickpocket and Alchemy, as well as a +10 bonus to Sneak, the ability to see in the dark for 60 seconds, and the use of their claws; this makes them great for stealth-based builds.
- BlazBlue: Taokaka the Cat Girl (it's not made clear how catlike she is under her hood, but she and the others from her clan definitely behave like cats) becomes an actual ninja (Bang's apprentice to be exact) in some joke endings.
- Ninja Cat is a free online flash game at Kongregate, where you play a cat who is a ninja.
- Final Fantasy XIV has the Miqo'te race, which are basically people with cat ears, tails and sometimes slitted pupils. The game also has a job called 'ninja'. So it's entirely possible to create yourself a cat-ninja in the game. The closest Non Player Characters get to this trope is probably V'kebbe the Stray, a former Pirate Girl who joined the Rogues' Guild.
- Moshi Monsters has a species of ninja cats called the Caped Assassins (they don't really kill people) who randomly disappear and reappear.
- Neko Atsume has the elusive Whiteshadow, who can appear in your yard at random, either "scouting" or doing "espoinage".
- Orcs Must Die Unchained has Midnight, a Cat Girl Ninja who serves the villain faction as a hired mercenary.
- Interestingly, being a Lombax, Ratchet from Ratchet & Clank sometimes flirts with this trope - despite being a hero who deals primarily in superior firepower. In the second game, Going Commando, he was shown in a ninja outfit in a presentation still about "stealth training", in Ratchet: Deadlocked one of the most difficult awards to obtain is the "Ninja Ratchet" skin (that actually boosts his abilities a little), and in All-4-One, he gets a ninja skin alongside Clank, Qwark, and Nefarious.
- Brought up in the Mean Kitty Song.
Mr. Safety: This little kitty is a ninja, always stalking my feet...
- RWBY gives us Blake Belladonna, who is a Faunus, a species that is mostly human but with a few animal-like traits. Downplayed in that while her moveset and penchant for stealth are similar to that of a ninja, the actual occupation doesn't seem to exist - even if the word "ninja" has been mentioned a few times. RWBY Chibi downright has a segment about Blake being a "Teenage Faunus Ninja Catgirl" who throws out smoke bombs shouting "Ninja vanish!".
- Adventure Time: In the episode "Jake vs. Me-Mow", a tiny mummy cat assassin named Me-Mow is tasked with killing Wildberry Princess. Armed with sharp claws, poison, and ninja-like ability, she proves to be quite a handful for Finn and Jake.
- In Kung Fu Panda: Legends of Awesomeness, Po encounters a group of cats who are master thieves. While not technically ninja (since they are from China) they use kunoichi style distraction, and disguise, and follow a lot of ninja tropes.
- Dark Kat has some purple-furred ninjas in the SWAT Kats episode "Razor's Edge," although they really only get one scene showcasing their martial arts skills.
- In a short animation called Neko, there is a sleek, slim, black ninja cat in Feudal Japan fighting a robot who stole his/her mouse. Turns out its the Imagine Spot of a large, fluffy, semi-longhaired, but also black cat in a house in an Alternate History 1940s Paris, France fighting a vacuum cleaner.