Kitty is Hettie Hubble's dog.
Story[]
In The Confidence Trick, the girls have to pass their broomstick flying test in order to stay at Cackle's. If they fail then they will be expelled from Cackle's. When the student witches pass, they get given a cat. When Hettie wishes she'd rather have a dog, Belladonna makes her wish come true by turning the dog her grandmother sent her into a cat. Miss Cackle then lets Hettie keep the dog.
She's quite happy about it, preferring dogs, and names the dog Kitty. Miss Cackle is very amused at the idea of a witch having a dog, and Hettie is allowed to keep her dog instead of being made to get a cat. Kitty is not ever seem accompanying Hettie on her broom, however.