Fuzzies are small, spherical creatures covered in spiky black hair. They have two "googley" eyes and a mouth full of blunt teeth. Fuzzies usually travel along line-guides, but there are also Fuzzies which follow along walls, though these were used in the original Super Mario World as Li'l Sparkies.. All Fuzzies will harm Mario when touched, and they are invulnerable to all of his attacks, even Stars! Invincible Mario will pass through them unharmed, however. If they are line-guided, Yoshi is also unable to eat them.
In later Mario games, most notably the Paper Mario series, Fuzzies also gained the ability to suck HP and heal themselves by the damage dealt. However, they aren't similar to Fuzzies in Super Mario World 2; those were completely different Fuzzies.
Line-guided Fuzzies are sprite 68, while ground-guided ones are sprite A5, the same as Sparky. Which graphics they will use depends on if the tileset is (01) Castle 1 or not. Fuzzies use palette A, and their graphics will only show up properly when the rope sprite set is used. (GFX05 loaded into SP4, in other words.)
Line-guided Fuzzies travel to the left or right depending on their X position. Take care when setting Fuzzies on line-guides, as if they're not situated perfectly, they can fly off the guide, so test thoroughly when using them.
If you edit GFX03 to replace Sparks with Fuzzies (or use ExGFX), the Fuzzies will look like they're going upside-down very rapidly!
|xDDF5||$01:DBF5||[C8] Line-guided Fuzzy tilemap|
|x1406B||$02:BE6B||[C8] Ground-guided Fuzzy tilemap|