Muggles' Guide to Harry Potter/Characters/Crookshanks

Overview
Crookshanks is a cat owned by Hermione Granger. He is quite large, for a cat, orange ("ginger") colored with brown stripes, and has an "ugly", almost flat face and a bottle-brush tail. Although his significance to the Harry Potter series is limited, readers have picked up traces of skepticism over his bearing. He is half-Kneazle, half-cat.

Prisoner of Azkaban
Crookshanks enters the story by jumping from the top of stacked cages in the Magical Menagerie in Diagon Alley, on to Ron's head, in an almost-successful bid to catch Scabbers. Hermione, who intended to purchase an owl, instead buys Crookshanks, over Ron's protests that Scabbers will never get any rest with "that cat" around, and takes him to Hogwarts. During the trip to Hogwarts, and several times over the school year, Crookshanks attempts to catch Scabbers, often damaging Ron in the process. At least once, Crookshanks seems to be deliberately eating a spider in front of Ron, which Ron sees as direct aggravation. Eventually, we are led to believe that Crookshanks fatally attacks Scabbers in the boy's dormitory.

Harry later sees Crookshanks in company with the large black dog that has evidently been following Harry around. This reassures Harry, who had believed the dog was a Grim; if Crookshanks can see him, the dog must be real rather than spectral.

As Ron, Harry, and Hermione are headed back to the castle after leaving Hagrid's hut, Crookshanks again attacks Scabbers, who was found alive. When Ron and Scabbers are dragged into a tunnel under the Whomping Willow by the mysterious black dog, Crookshanks shows how to still the Willow so Harry and Hermione can follow.

In the Shrieking Shack, it is revealed that Crookshanks befriended Sirius Black, an Animagus wizard who can communicate with Crookshanks while in his dog form. It was Crookshanks who stole the password list from Neville Longbottom, allowing Sirius access into the Gryffindor Common Room the night Ron was supposedly attacked, though Scabbers was the actual target. Several times during the ensuing scuffle in the Shack, Crookshanks defends Sirius against Harry: attacking Harry when he tries to recover his wand, and sitting on Sirius' chest exactly where Harry needs to fire a killing spell at Sirius.

As they exit the shack and Lupin turns into a werewolf, Peter Pettigrew seizes Ron's wand and uses it to stun Ron and Crookshanks before making his escape.

Finally, when Sirius gives Ron a new owl, Ron holds it under Crookshanks' nose for approval before accepting it. Ginny names the owl Pigwidgeon.

Goblet of Fire
Crookshanks is at the Burrow with Hermione. We see him chasing gnomes in the garden before dinner. When Fred Weasley drops some fireworks as the family prepares to depart for London and the Hogwarts Express, Crookshanks is frightened and mauls a Muggle taxi-driver. He rides in the same taxi as Harry, Ron, and Hermione, and all three get rather badly scratched.

On the Express, and throughout the book, Crookshanks is an occasional presence, curled up on a chair, jumping into either Harry's or Hermione's lap, and generally behaving as a cat should. Crookshanks seems to be quite willing to soak up almost any amount of affection from either Harry or Hermione, and sometimes Ginny, but does not seem to entirely trust Ron.

Order of the Phoenix
At Number 12, Grimmauld Place, we see Crookshanks in the kitchen, playing with Butterbeer corks, and generally acting like a cat. Throughout the book, Crookshanks is an occasional presence, curled up on a chair, jumping into either Harry's or Hermione's lap, and generally behaving as a cat should.

Half-Blood Prince
It is mentioned that Crookshanks accompanies Hermione to the Hogwarts Express when they leave The Burrow. Once again, Crookshanks seems to be acting like a cat, and having only a passing role in the story.

Deathly Hallows
We see Crookshanks at Hermione's feet when she, Ron, and Harry manage to sneak some time together in amidst the wedding preparations at The Burrow. Crookshanks, here, is behaving very much like a cat, simply lying, curled up, at Hermione's feet while she sorts books. When Mrs. Weasley bursts in on them, Crookshanks, bristling, dashes under the bed to hide.

When Harry, Ron, and Hermione need to enter the tunnel at the base of the Whomping Willow, Ron wishes that they had Crookshanks with them to push the knot that will still the tree. In words strongly reminiscent of something Ron had said in the first book, Hermione says, "Are you a wizard, or what?" Ron, recollecting himself, uses the first charm he ever learned (Wingardium Leviosa) to push a stick against the knot that stills the Willow.

Strengths
Events in Harry Potter and the Prisoner of Azkaban show that Crookshanks is far more intelligent than the average cat. We don't initially notice this, as all wizard's companion animals, including Hedwig, Trevor, Scabbers, and (later) Pigwidgeon, seem much more intelligent than their Muggle equivalents. While Scabbers' intelligence is explained when his true nature is revealed, Crookshanks' intelligence can only be inferred to be the product of his being a cross-breed with a Kneazle.

Being half-cat, Crookshanks is always armed, and is clearly not afraid to use his claws and teeth when he feels the need.

Weaknesses
Crookshanks' ability to communicate, naturally, is limited by his being a cat.

Relationships with Other Characters
Crookshanks is Hermione's cat; they are quite fond of each other. When Hermione first bought Crookshanks, the witch at the Magical Menagerie told her that he had been there for quite a while; the implication being that very few other witches or wizards were interested in him, or perhaps he in them. The author, describing the genesis of the character, says that he is based on a Muggle cat who would prowl around the sunbathers in a particular square, looking disdainful and refusing to be stroked. While she says that she only borrowed his appearance for Crookshanks, perhaps that character trait also crept in, at least in the beginning.

Crookshanks is perpetually trying to attack Scabbers, who is Ron's pet rat. Initially he seems to be doing this because he simply doesn't trust Scabbers (he may be able to detect that Scabbers is not what he seems to be). Later, it seems he is trying to fetch Scabbers at the bidding of Sirius Black, who has recognized Scabbers as Peter Pettigrew and wants to get him away from the protection afforded him by Hogwarts. Ron, of course, is trying to defend Scabbers from Crookshanks, and gets into the middle of the battles quite often; as such, at least in Harry Potter and the Prisoner of Azkaban, the two of them are quite often fighting each other, and this almost rabid dislike has left enough bad memories that, while Ron can respect Crookshanks and his abilities, they are never quite comfortable with each other.

With other people, Crookshanks is more neutral, accepting affection and being willing to play. He is quite classically cat-like both with Harry and with Ginny Weasley, climbing into laps for a quick nap and playing with Butterbeer corks.

Analysis
Crookshanks' apparent extreme intelligence, as displayed in Harry Potter and the Prisoner of Azkaban, coupled with his flattened face, has led more than one reader to believe that he might be an Animagus, possibly even Regulus Black. There is precedent in the series for an unregistered Animagus, believed dead, to have stayed in his animal guise for several years. However, the author has denied this; in fact, she has stated, while discussing his origins, that Crookshanks is half Kneazle.