The books in the series:
- Thora (published in the U.S. as Thora: A Half-Mermaid Tale): 2003
- Thora and the Green Sea-Unicorn (2005)
- Thora and the Incredible Crystals (2007)
The Thora books contain examples of:
- Brits Love Tea: Mr Walters is English, and celebrates good occasions with a cup of tea. When the characters go to London in The Green Sea-Unicorn, Mr Walters is so happy to see his hometown again that he drinks an entire pot of tea.
- Disappeared Dad: Thora's human father, Thor, disappeared five days into her parents' marriage.
- Dream Reality Check: In the first book, Thora pinches herself when she learns that Dottie is her grandmother.
- Embarrassing Last Name: In The Green Sea-Unicorn, Thora and her family stay with Mr Walters' godson Jerome Bidet and his daughter Louella. Louella hates having a name that's French for toilet. When she grows up, she plans to change it to her mother's maiden name, Rose.
- Family Eye Resemblance: In the first book, Dottie Greenberg tells Thora that her eyes are the same shade of green as Thor's.
- Forging the Will: In The Green Sea-Unicorn, Louella's father and stepmother plan to allow the croquet player Ricardo le Drone to build five Olympic-sized croquet courts on their estate in order to make it the setting of a reality show focused on croquet hooligans, in accordance with the wishes of Louella's late grandfather Lionel. But then a lawyer finds that Lionel's will was amended to give Ricardo permission to build the croquet courts several hours after he died, meaning that Ricardo forged it.
- Fountain of Youth: The Incredible Crystals focuses on crystals that can reverse aging. Madame Pong first discovers the effect when her geriatric pug eats one and his many health problems vanish in seconds. Now the Deep Breath Hotel and Spa, which she owns, has become extremely wealthy by marketing crystal-studded tubs. Unfortunately, the crystals can have a number of side effects - Adelaide and Bruce have lost all their hair and suffer from a constant sense of deja vu, while Mr Walters becomes briefly obsessed with health to the exclusion of all else.
- Free the Frogs: In The Green Sea-Unicorn, Shirley the sea-unicorn helps Miss Fishlock escape from a shipwreck. Miss Fishlock is so grateful that she promises to help Shirley with whatever she wants, which turns out to be breaking fish out of aquariums, making sure to only take fish that can survive in the water near England. Every time Miss Fishlock and Shirley strike, Miss Fishlock leaves a note in lipstick, like "GONE HOME."
- Godiva Hair: Illustrations show Halla as having this.
- Hide Your Otherness:
- For most of Thora's childhood, Halla was a champion open water swimmer who wore a special wetsuit called a Halla-Skin to make it look like she had legs instead of a tail.
- Halla teaches Thora how to keep the purple scales on her legs and feet covered, and wear a ponytail to hide the blowhole on her head.
- The Green Sea-Unicorn has the mermaid Pamela Poutine, who left the sea and moved to London to become an actress. She drags herself around on crutches, and wears long skirts with hoops to hide the shape of her tail.
- Homeschooled Kids: Thora was homeschooled by Mr Walters, who has already taught her calculus.
- Identity Amnesia: As punishment for falling in love with a mermaid, the Sea Shrew erased Thor Greenberg's memory and banished him to a tiny island near Australia. The spell isn't broken until Halla finds him almost twelve years later.
- I Have No Son!: After Thora was born, Halla went to her family for help, but her father shouted, "I have no daughter! Take her away!"
- Limited Wardrobe: Thora always wears a Halla-skin, a kind of wetsuit designed to hide her mermaid ancestry.
- Long-Lost Relative: In the first book, Thora learns that Dottie Greenberg is Thor's mother and her grandmother. She's thrilled to finally have an extended family.
- Minor Living Alone: In the first book, the Loki docks at the seaside town of Grimli, where Thor used to live. To avoid being seen, Halla lives on a barren island appropriately named the Rock five miles away from shore. Mr Walters has to go to Argentina to attend a relative's funeral, leaving Thora alone on the boat most of the time. Local busybody Mrs Grubb unsuccessfully tries to get her placed in foster care.
- Our Phlebotinum Child: Adelaide and Bruce Ferguson from The Incredible Crystals put off having a child until Bruce's cricket career was over, only to find that they had waited too long. Madame Pong let them use their tubs to de-age themselves until they could have Felicity.
- Parental Substitute: After Thora was born, she wouldn't eat mermaid food, and Halla couldn't figure out how to feed her. Mr Walters heard her crying and got her some milk to drink. He stayed on the Loki to help raise her, since he was retired and had no other responsibilities. He taught her almost everything she knows, and treats her like his granddaughter.
- Prank Call: In The Incredible Crystals, Felicity, whose parents work at the Deep Breath Hotel and Spa, likes to annoy guests by calling their rooms and making loud farting noises.
- Prefers Going Barefoot: The Incredible Crystals has six-year-old Felicity Ferguson, who almost never wears shoes because she thinks they're too much trouble. She doesn't worry about all the spiders and snakes in her area because she thinks they're more scared of her than she is of them.
- Saving the Orphanage: In the first book, the villainous developer Frooty de Mare is trying to buy up all the beachfront properties in Grimli so he can knock down the buildings and replace them with his own businesses, which include a casino, a hotel, and a restaurant. The one holdout is the Allbent Cinema, whose owners, Lottie, Flossie, and Dottie Greenberg, refuse to sell. In an effort to put them out of business, Frooty creates his own cinema, where he screens pirated movies to save money.
- Shared Family Quirks: Thora often scratches her elbows. She learns that Thor had the same habit.
- Signature Scent: Halla's hair smells like pumpkin pie, a food she'd never heard of before she met Thor.
- Taking the Kids: In the first book, Thora gives a figurine found by Halla in a river to her friends Ricky and Lynne Rukle. Their mother sells the figurine and uses the money to move with Ricky and Lynne into a new house, leaving her husband, whose gambling habit has been keeping the family in poverty.
- Tropey, Come Home: Cosmo goes missing in The Incredible Crystals. He was abducted by Adelaide because peacock feathers are used in manufacturing squidgy dinosaurs. Thora and Felicity find him locked in a hangar with almost forty other naked peacocks.
- Unable to Cry: Mermaids don't cry. Instead, their tails become pale when they're sad.
