As a result of storing too much electricity, it developed patches where even downy wool won't grow.
Its fluffy fleece easily stores electricity. Its rubbery hide keeps it from being electrocuted.
Because of its rubbery, electric ity-resistant skin, it can store lots of electric ity in its fur.
FLAAFFY’s wool quality changes so that it can generate a high amount of static electricity with a small amount of wool. The bare and slick parts of its hide are shielded against electricity.
Its fleece quality changes to generate strong static electricity with a small amount of wool. The bare, slick parts of its hide are shielded against electricity.
— Pokédex entries (via PokeAPI)