All Girls Want Bad Boys: Subverted. She hits it off with a man dressed as Dracula at the PTA dance. Then when it's discovered he's just a school inspector...she's still very interested.
All Witches Have Cats: She has a china cat she calls Hecate, but her main pet is a rat called Herbert.
Babies Ever After: After the Time Skip in You're Kidding, Ms Wiz, she's the mother of a one-year-old called William.
Blithe Spirit: She comes to liven things up whenever they're needed.
Companion Cube: Hecate again, though the thing is actually sentient.
Cool Teacher: In the first book only, as she's no longer a teacher after that. She does become principal briefly in Ms Wiz Banned.
Real Men Wear Pink: He loves football, skateboarding and everything boyish - and owns most of Beatrix Potter. He's near tears when Peter Rabbit (freed from his book) gets squashed by a bus.
Peter "Podge" Harris:
Abusive Parents: His dad is very stern and mocks his son's weight.
Big Fun: His own father describes him as "like a football on legs".
A Day in the Limelight: Power Crazy Ms Wiz - where he has to worry about his father making him transfer schools. Also Ms Wiz Smells A Rat where he has to hide Herbert in his house.
Characterisation Marches On: The first book describes her as the class dreamer. This trait never shows up again.
A Day in the Limelight: Ms Wiz Goes Live - where Ms Wiz takes her and her sister to a TV studio.
Hilariously Abusive Childhood: Her parents have no problem arguing in front of their daughters. Caroline gets freaked out when the aftermath of a spell has them holding hands.
I Am Very British: Pulls this voice off to imitate Fergie and fool the Chief Leisure Officer.
Man of a Thousand Voices: Female example. In Control Ms Wiz reveals that she's very good at faking voices.
Only Sane Woman: She's usually the voice of reason. Ms Wiz Goes Live has her getting annoyed with being expected to be mature all the time.
Wise Beyond Their Years: Deconstructed. She resents having to be the sensible one, feeling she never gets to cut loose or have fun as a result of everyone's expectations.
Katrina O'Brien:
Beauty Contest: Her parents enter her in one in Ms Wiz Supermodel.
A Day in the Limelight: Despite being introduced in Book 1, she doesn't get one until Ms Wiz Supermodel (the eleventh book) - where she enters a child fashion show.