From the Super Mario Wiki
Fuzzies, also called Fuzzles, are small, black-furred parasitic creatures capable of sucking away enemies' health with a bite. They possess two strabismus eyes and large teeth. Despite displaying some level of intelligence and the ability to speak, Fuzzies are, for the most part, wild and uncivilized beings. Fuzzies have the ability to secrete webbing-like strands from their bodies, though this ability has largely been phased out in modern times.
Super Mario series
Super Mario World
Fuzzies first appear in Super Mario World as particularly rare enemies that cannot be defeated, found circling the wire-like constructs floating in mid-air or blocks. Fuzzies do not directly attack Mario or Luigi and do only hit them if they get in their way. The ones circling around blocks can be defeated, either by Yoshi or by tossing a Koopa Shell at them.
New Super Mario Bros. Wii
Fuzzies, along with bigger versions called Mega Fuzzies, neither of which were named in the Prima Games guidebook, reappear in the game New Super Mario Bros. Wii where they are found in Worlds 7 and 9. They act the same way as they did in Super Mario World. Unlike in Super Mario World though, they can be defeated by being frozen and shattering the block of ice they're trapped in or blasting them with fireballs as Fire Mario. Fuzzies can also be found on wires and are mostly in sky levels. They are usually found in big groups, and they also do flips when they jump from one wire onto another.
Super Mario Galaxy 2
Fuzzies appear in Super Mario Galaxy 2. They first appear in the Honeybloom Galaxy, moving up and down the orange poles that Mario or Luigi can climb. Fuzzies are also found in the Flipsville Galaxy, where they can be defeated with a Spin Drill. They look very similar to how they did in New Super Mario Bros. Wii, though they leave behind black smoke clouds as they move.
There is a species that behaves like Fuzzies by latching onto characters and draining their HP, known as Slurples. Slurples also appear in Super Mario Galaxy 2, as well as its predecessor, Super Mario Galaxy.
Super Mario 3D Land
New Super Mario Bros. 2
Fuzzies appear in New Super Mario Bros. 2, acting the same way as in New Super Mario Bros. Wii. They can be defeated by shooting them with a fireball, using a Star, using a Super Leaf tail whack, or using a Gold Flower. They appear in World 2-A and World 4-C.
New Super Mario Bros. U
Super Mario 3D World
Fuzzies reappear in Super Mario 3D World. In this game, they have the ability to move without the aid of a line. They are generally found in Shadow-Play Alley and moving through and around Clear Pipes. Like in previous games, they are almost invincible, as they can only defeated by a Super Star, Golden Statue Mario, or a potted Piranha Plant.
In World 6-7, Fuzzy Time Mine, an enormous swarm of Fuzzies pursues the characters. These Fuzzies just serve as a wall that causes damage upon contact, similarly to Munchers from Donkey Kong Country Returns.
Super Mario Adventures
Fuzzies make a return appearance in Paper Mario, which reveals a large group of them inhabit the woods behind Koopa Village. Fuzzies attack by draining HP from Mario. When Mario first reaches Koopa Village, he finds it under attack by a horde of Fuzzies who are harassing the Koopa Troopa inhabitants of the village. After Mario defeats the apparent leader of the Fuzzies, who stole the Shell of Kooper, after the battle, the Fuzzies promise to behave and stop attacking the village, at least, for a while. A Fuzzy can also be fought in Shy Guys Toy Box if Princess Peach tells Bowser that a Fuzzy is one of Mario's worst fears, Kammy Koopa will then warp one into the Toy Box to guard a Treasure Chest and defeat Mario.
A similar enemy known as the Swoopula acts and attacks like a Fuzzy.
Also, an aqua colored Fuzzy was intended to appear, but never it made the final version.
Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, Fuzzies appear as semi-common enemies, first appearing in Shhwonk Fortress and later, one appears as a member of the Fuzz fighting team in the Glitz Pit. They also appear in the first floors of the Pit of 100 Trials. They attack the same ways as they did in the previous games. The Forest and Island Fuzzies from the previous games are replaced by the functionally identical Green Fuzzy and Flower Fuzzy.
Super Paper Mario
In Super Paper Mario, Fuzzies appear as enemies on the Planet Blobule, where unlike their previous appearances, instead of draining HP, they attack other creatures by bouncing into them. The most dangerous type of Fuzzy called a Dark Fuzzy is introduced in this game.
Paper Mario: Sticker Star
Fuzzies make another appearance in the Nintendo 3DS game Paper Mario: Sticker Star. They only appear in level 4-5, Whiteout Valley, where they ride the ski lift bar, coming from the front and back. Once a Fuzzy reaches Mario, it will jump up and fall onto Mario unless he swings his chair out of the way. Fuzzies often appear in groups of 2-4. In battle, all a Fuzzy can do is simply bounce and slam into Mario. However, if a Fuzzy is hit and not defeated, it will multiply into two Fuzzies, similar to their multiplication powers in previous Paper Mario titles. In world 1 of this game, the first level called Warm Fuzzy Plains is the same though Fuzzies did not appear in this level.
Mario Party: Island Tour
Fuzzies once again make an appearance in Mario Party: Island Tour, in the minigame Buzz a Fuzzy. The player has to use the suctions to capture as many Fuzzies as they can. A Fuzzy also appears as one of the tiles in the minigames Match Faker and Tap Dash.
Mario & Luigi: Superstar Saga
Mario Kart 8
Captain Toad: Treasure Tracker
Mario Party 10
In Mario Party 10, Fuzzies appear in multiple minigames.
Paper Mario series Stats & Tattle Information
Names in other languages