Regular Fuzzies are black, but there are different types that come in different colors, each with different ways of attacking. Common Fuzzy behavior includes lingering and traveling along the line of a moving platform and absorbing health from Mario. They are limbless, and move by hopping around when not attached to a line. The outline of a Fuzzy seems to always be moving. Fuzzies have asymmetrical eyes with pupils that move rapidly, and very few, square teeth.
In the games
Super Mario World
In Super Mario World, Fuzzies are found in forest levels and are a threat to Mario because they move along the wire in which platforms also travel. Fuzzies could only be defeated with invincibility, Koopa shells, or fireballs, are are hard to hit nonetheless.
Fuzzies aren't seen again until Paper Mario, where they have gained the ability to sap health to replenish their own. Black Fuzzies are the basic types, encountered in Chapter 1. They were responsible for mischief in Koopa Village and eventually fled once they were pummeled by Mario. Paper Mario also introduce two new types of Fuzzies: Forest Fuzzies, green in color, native to Forever Forest, and Jungle Fuzzies, yellow in color, native to Yoshi's Island's beach and Jade Jungle. A character named Fuzzipede might be related to Fuzzies, as he moves, looks, and attacks similarly.
Mario & Luigi: Superstar Saga
Paper Mario: The Thousand-Year Door
Fuzzies reappear in Paper Mario: The Thousand-Year Door, again as enemies in the beginning of the game. This time, they are led by a Gold Fuzzy, who ironically lacks the ability to sap health like his minions. They aid him in fighting against Mario as he tries to retrieve the Moon Stone from them in Shhwonk Fortress. After they are defeated, they flee, like they did in Paper Mario, along with their leader. This game introduced new types of Fuzzies along with Gold: Green Fuzzies, Forest Fuzzy-like Fuzzies that are simply stronger variants of regular Fuzzies, and Flower Fuzzies, pink in color, which sap Mario's FP rather than his HP.
Super Paper Mario
Fuzzies make another appearance in the Paper Mario series games in Super Paper Mario. Here, they attack the way they do in the previous games, and are found only in Planet Bobule. Like all other enemies in this game, they have pitch-black counterparts, called Dark Fuzzies, that are stronger and appear in Flopside's Pit of 100 Trials.
New Super Mario Bros. Wii
Fuzzies appear in New Super Mario Bros. Wii, returning to their behavior from Super Mario World. This time, they are known to travel in groups, and are overall difficult to evade.
Super Mario Galaxy 2
Super Mario Galaxy 2 marks the Fuzzies' first 3D platformer appearance. They act generally the same way they do in Super Mario World and New Super Mario Bros. Wii, except they only appear on side-scrolling missions.