Kitten

Kittens are a species of small cats that appear in Bowser's Fury. They can be seen on most of the various islands composing Lake Lapcat. They exist in five different colors: green, red, blue, black, and, each representing the different colors of the  (lucky cat). The former four also match the Cat form colors of the playable characters in Super Mario 3D World other than Mario: respectively Luigi, Peach (although using a deeper shade of pink similar to Toadette's Cat form), Toad, and Rosalina.

Kittens can be seen relaxing, grooming themselves, or playing with baseballs in various spots in Lake Lapcat. If there is a shell nearby, kittens will lunge at it, knocking the shell forward little by little. They are friendly, and follow and affectionately nuzzle Mario if he is in his Cat form or Lucky Cat form, though they do not follow him into water. If Mario approaches them in any other form, however, they become frightened and try to avoid him. They can also be picked up and carried by Mario. While being carried, they will continuously scratch in front of them, which can destroy Brick Blocks and activate ? Blocks, similarly to Cat Mario's scratch. Kittens will bounce on Mushroom Trampolines and Jump Panels, and cause Donut Blocks to fall, similarly to Mario. If a kitten makes contact with water or lava, it will vanish and respawn at its original location. If Mario or Bowser Jr. attack a kitten, it does not take damage, and confetti appears instead.

Although the plain-colored kittens are not related to any game objective, the calico kittens are missing offspring of Oyaneko that must be returned to them for Cat Shines. There are nine calico kittens across Lake Lapcat: one near the Lakeside Giga Bell, three near the Ruins Giga Bell, and five near the Wasteland Giga Bell. Some are located close to their parent, while others require Mario to carry them a great distance back.

After beating the game once, Cat Plessie becomes able to carry kittens if Mario throws them on top of it or mounts it while holding one, allowing them to travel to different islands.

In the game's ending, three kittens (blue, pink, and green) run off after Bowser lands near them following his defeat as Giant Bowser. After Bowser and Bowser Jr. depart, these kittens circle around Cat Mario. The blue kitten nuzzles Mario, and the pink kitten licks its paw. The three kittens and Mario then jump up into the air.

Excluding calico kittens, there are 41 kittens in total: four near the base of Scamper Shores, four on a higher hill in the same area, four in a tunnel behind Fort Flaptrap, four near the lighthouse of Pounce Bounce Isle, four near the lighthouse on Roiling Roller Isle, four on Mount Magmeow, three at the top of Pipe Path Tower, and fourteen around the Wasteland Giga Bell.

While Fury Bowser is active, all kittens become corrupted and attack Mario, regardless of his form. If Mario is holding a kitten when Fury Bowser wakes up, then he will be damaged and drop it. If a kitten is riding Plessie when Fury Bowser wakes up, then it will teleport back to its original location.

In Super Smash Bros. Ultimate, kittens were added as a Novice-class support spirit during the five-day "Bowser's Fury" spirit event that began on April 9, 2021. When equipped, they reduce the fighter's weight but increase their speed. In their spirit battle, they are represented by five different-colored Kirbys equipped with Super Leaves, and the battle takes place on the Warp Pipe island in Delfino Plaza, referencing Lake Lapcat. The arrangement of Super Mario 64's main theme from Super Smash Bros. for Nintendo 3DS / Wii U serves as the battle's music.

Lakeside Giga Bell

 * Found on the other side of the Giga Bell where the Oyaneko is located.

Ruins Giga Bell

 * Found in a corner near the Clear Pipe Cannon that takes Mario back to the top of Slipskate Slope.
 * Found on top of the cat-shaped gate to Clawswipe Colosseum.
 * Found near the entrance to Crisp Climb Castle.

Wasteland Giga Bell

 * Found on the opposite side of the Wasteland where the Oyaneko sits.
 * Found on a pier with Dash Panels on it at the beginning of the Wasteland area.
 * Found near the entrance to Pipe Path Tower.
 * Found inside an alcove underneath the entrance to Risky Whisker Island.
 * Found near the lighthouse of Mount Magmeow.