Tabby is Mildred's cat through her years at Cackle's Academy and Weirdsister College. Every witch was originally intended to have a black cat each, but since Miss Hardbroom found it unlikely that Mildred would ever pass the test, she didn't get a cat for her. Fortunately, she succeeded and the school granted her a gray and stripy cat which she named Tabby.
Star is Mildred's Dog, who she finds in her fourth year at Cackle's. Mildred trains star on her broomstick, Star becomes Mildred's broomstick companion after his tricks win the talent competition for Cackle's.
Midnight is Maud's cat, mentioned in the First Worst Witch book. The name was chosen, appropriately, at midnight, when Maud and her best freind Mildred Hubble were chatting about getting their kittens the next day. Midnight is not that good at flying, though she is better at it than Tabby. In fact, she started in about the same place as Tabby stayed at throughout the series. Like most cats, she is put to doom by Ethel Hallow's cat Nightstar. Midnight is described as a normal, easygoing black cat.
Stormy is Enid's cat, mentioned by name in The Worst Witch to the Rescue but renamed Teaser in the television series. Enid was training her to jump from the top of the wall onto her broom as it passed below at speed. Fortunately, Stormy was rather bold, unlike most cats, and wasn't bothered by sudden movement. Stormy really enjoyed this manoeuvre and was happily jumping from the wall, landing perfectly on the broom, zooming around the yard, and leaping back on the wall, supervised by a proud Enid.
Nightstar is Ethel's cat, mentioned in the First Worst Witch book. Like most of the other cats, he is black all over. Nightstar is very good at flying. He sits on Ethel's broomstick as if he is a model glued down. He is so good that he puts all the other cats to shame. Even when not on the broom, Nightstar sits bolt upright and still like a statue. Nightstar is very protective and territorial of Ethel and her broomstick. When Mildred's cat Tabby ended up on Ethel's broomstick, he kept on swiping down on his guest.
Morgana is Miss Hardbroom's cat. Morgana was mentioned in The Worst Witch All At Sea. She is also mentioned (though not by name) in The Worst Witch Strikes Again, when Mildred accidentally pole vaults through HB's window and when Miss Cackle starts to tell her off, she is also 'removing a jam tart from her shoulder and absent mindedly feeding it to Miss Hardbroom's cat.'
Morgana is described as a particularly beautiful, sleek black cat with olive-green eyes.
Ebony is Fenella Feverfew's cat. Ebony belongs to Harriet Goodcharm in the TV series. In The Worst Witch All at Sea, Miss Cackle suggests to Mildred that she replaces Tabby. A third-year witch, Fenella/Harriet, transferred to Miss Pentangle's Academy several mountaintops away and left behind her sleek black cat, Ebony, since they have owls at Miss Pentangle's instead of cats.
Ebony is almost as good as Ethel's Nightstar.
Lightning is Mrs Tapioca's cat, not really a witches cat, though she is Tabby's mother. Mrs Tapioca says that Lightning is "named right- "fast as lighting to take tinned food from bowl, but not mice!"
Kitty is a dog rather than a cat, but is Hettie Hubble's pet in The New Worst Witch. In episode 2, 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. When the student witches pass, they are 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 in order to get her in trouble when it changes back. Miss Cackle then lets Hettie keep the dog, to the disappointment of Belladonna, whom Hettie names Kitty.