Crookshanks was Hermione Granger's pet cat. He was half-Kneazle, as evidenced by his lion-like appearance, ability to solve problems on his own without aid or teaching, and clear dislike of and ability at recognising untrustworthy persons (even if they are transfigured).
In 1993 Crookshanks was purchased from Magical Menagerie by Hermione Granger. The saleswoman from whom she had purchased him stated that he had been in the shop for a long time as "nobody wanted him".
 
Dimensions: 18 inches in length