But the word "fluffy" is an adjective, isn't it?Yes.
You are matter. I am matter. Fluffy is matter.
It certainly can be, but as emsr2d2 said, in this case it's a name. It's not uncommon to use an adjective as a name for a pet - Fluffy, Goofy, Red, Squeaky, etc.But the word "fluffy" is an adjective, isn't it?
It doesn't always work out that way.
IWe had a cat with one eye and a broken tail.
He lost his eye in a fight with another tomcat and broke his tail when it was run over by a bike.
His name was Lucky.