Har det någonsin avslöjat vad Crookshanks är?

Yep; Crookshanks är halv-Kneazle.

Från JK Rowlings webbplats :

Crookshanks, as anybody who has read Fantastic Beasts and Where to Find Them will have guessed, is half Kneazle. And if you don't know what a Kneazle is, you need to hurry up and buy Fantastic Beasts and Where to Find Them (all royalties go to help some of the poorest children in the world).

Du kan också kolla Crookshanks sidan på Harry Potter Wiki .

Crookshanks är halva Kneazle.

J.K. Rowling antyder först detta i hennes beskrivning av en Kneazle i Fantastiska djur och var att hitta dem och i en kommentar på hennes gamla hemsida.

Kneazle
M.O.M. Classification: XXX

The Kneazle was originally bred in Britain, though it is now exported worldwide. A small catlike creature with flecked, speckled, or spotted fur, outsize ears, and a tail like a lion’s, the Kneazle is intelligent, independent, and occasionally aggressive, though if it takes a liking to a witch or wizard, it makes an excellent pet. The Kneazle has an uncanny ability to detect unsavoury or suspicious characters and can be relied upon to guide its owner safely home if they are lost. Kneazles have up to eight kittens in a litter and can interbreed with cats. Licences are required for ownership as (like Crups and Fwoopers) Kneazles are sufficiently unusual in appearance to attract Muggle interest.
(Fantastic Beasts and Where to Find Them)

Neither of these characters can perform magic (Filch’s Kwikspell course never worked), but they still function within the wizarding world because they have access to certain magical objects and creatures that can help them (Arabella Figg does a roaring trade in cross-bred cats and Kneazles, and if you don‘t know what a Kneazle is yet, shame on you).
(JK Rowling's old website - Extra Stuff - Miscellaneous - Squibs)

Hon sa också detta direkt på hennes hemsida och sedan senare på Twitter.

Crookshanks, as anybody who has read Fantastic Beasts and Where to Find Them will have guessed, is half Kneazle. And if you don't know what a Kneazle is, you need to hurry up and buy Fantastic Beasts and Where to Find Them (all royalties go to help some of the poorest children in the world).
(JK Rowling's old website - Extra Stuff - Characters - Squibs)

Spooky Magdalen: who would win in a fight, Mrs. Norris or Crookshanks?
J.K. Rowling: It would be brutal and very close, but Crookshanks' Kneazle ancestry would bring him out on top.

Och inte att den nuvarande Pottermore har någon äkthet än wikien, men de bekräftar detta på deras faktablad på Crookshanks.

Hermione’s sharp-witted pet cat, who is half-Kneazle