According to the Hogwarts supplies list, students are allowed to take an owl or a cat or a toad. However, Albus took a ferret and an owl to Hogwarts. The rule may have been changed by 2017. However, there were exceptions to this rule during the 1990s, including rats (which might have changed by 2017) and Pygmy Puffs (which were owned by Albus' uncle and mother, respectively). 
 
Ferret plush puppet with soft faux fur features a movable head and mouth. 
Dimensions: 14 1/2"L x 7"H