The protagonist of the story, a brave and irascible (in her own words) Nebraska girl who was swept away from her kitchen by the Green Wind and brought to Fairyland to have adventures.
- The Chosen One: The story flirts with this concept, but ultimately subverts it. The Green Wind points out that it was September herself who decided to go on a quest for Goodbye's spoon and all the adventures that followed; she could have done what other children do in Fairyland and had fun, but she didn't.
- Deal with the Devil: September is tempted by a pair of shoes offered by the Marquess as thanks for going on a quest for a magical sword.
- Distinguishing Mark: The mole on September's cheek. This is how people recognize her relation to Halloween and how Saturday recognizes their daughter.
- Food Chains: September is warned not to eat any of the food in Fairyland, or else she risks becoming like Persephone. She fails to properly heed this warning, but it ends up working out for the best.
- The Hero's Journey: September's path through the first two books, though her journey each time is very different.
- Heroic Sacrifice: September sacrifices her shadow to save a Pooka girl's life.
- I Just Want to Be Special: September is afraid she isn't special enough for the Green Wind to bring to Fairyland. Through the rest of the first book she wonders if she is brave enough to be a proper heroine.
- Jumped at the Call: When the Green Wind invites September to Fairyland, she doesn't need to be asked twice.
- Loners Are Freaks: September didn't have any friends before going to Fairyland, and going only makes her stranger to the other kids.
- Nice Job Breaking It, Hero!: September trading her shadow for the Pooka girl did in fact save that girl's life. It also later ended up putting Fairyland in great danger.
- Screw Destiny: In the third book she smashes her fate.
- Sympathy for the Devil:
- When she learns how unfair the Marquess' lot really was, September can't help but feel sorry for her. She doesn't want to, but pity eventually erodes her hatred of the villain.
- September acknowledges everything Halloween did is what she herself wished she could do, and decides holding her at fault would be too hypocritical.
- Trademark Favorite Food: September has a weakness for pumpkin. It's why orange is her favorite color in fact.
- Wrench Wench: September learned from her mother how to fix machines. This is especially apparent in The Girl Who Raced Fairyland All the Way Home when she becomes queen of Fairyland under the title Engineer.
- Wrong Genre Savvy: September thinks she knows what to expect of Fairyland, but she is constantly proved wrong. This is lampshaded early on when she tries to figure out what sort of story she is in, and can't decide.
The Green Wind
A man dressed all in green riding a wild cat.
- Herald: He's the one who draws September into Fairyland in the first place.
A wyvern, and one of October's closest Fairyland friends. Oh, and hes half library, too making him, in the book's words, a wyverary.
- Meaningful Name: As his name indicates, he boasts an Encyclopaedic Knowledge of any subject if it happens to start with the first twelve letters of the alphabet.
- Our Dragons Are Different: Ell is a wyvern, a species of dragon with no forefeet, and (possibly) half a library.
- Red Oni, Blue Oni: The red oni to Saturday's blue oni, and colored to match. Ell is loud and quick to threaten to burn things down if he thinks harm may come to September.
A Marid and one of September's closest Fairyland friends. Having been kept in slavery and horribly abused by the Marquess, Saturday is timid and shy, though he's deeply brave and loyal. Late in the first book it's revealed that he and September will marry, or at least have one daughter.
- Our Genies Are Different: Marids. Djinni are creatures of the air, but Marids are creatures of the sea, and they can only grant wishes after they lose a wrestling match.
- Red Oni, Blue Oni: The blue oni to Ell's red oni, and colored to match. Saturday is soft-spoken and gentle and hates granting wishes because he must wrestle and he's not allowed to hold back.
- Shrinking Violet: Saturday always keeps his emotions to himself. His shadow finds this irritating and is far more forward, especially when it comes to his feelings for September.
A Tsukumogami, a living lamp who previously lived with others of her kind on an island apart from mankind. She joined September on her quest in the first book after helping to comfort and rescue her.
- Animate Inanimate Object: It's her nature as a Tsukumogami, an object that gains sentience after one-hundred years. Gleam is one-hundred twelve when September meets her, making her a child by her race's standards.
- I Choose to Stay: September asks Gleam to come with her when they reunite in the second book. She declines, as she enjoys traveling Fairyland Below on the Electric Eel Train.
- Talking with Signs: In a way. Gleam communicates by shining a light with a silhouette of the words she wants to say.
The Marquess / Queen Mallow / Maud Elizabeth Smythe
The ruler of Fairyland at the time of the first book a fearful woman with a childlike appearance who reigns through fear.
- Abusive Parents: Maud's father.
- Became Their Own Antithesis: The Marquess used to be, a long time ago, the good Queen Mallow
- Black Magician Girl/Lady of Black Magic: The Marquess combines elements of these, having the body of a child but the manner of someone much older.
- Came Back Wrong: A variant. The death involved is more metaphorical than literal. Mallow originally came to Fairyland an ordinary little girl who grew up to become a queen. When forced to leave, she desperately looked for another way in, despite no such way existing. It was only through turning her clock back—not at all unlike cheating death—that she could come back. As a very angry, bitter woman in a twelve-year-old girl's body.
- Creepy Child: The Marquess, who has no problems killing and threatening others and is physically twelve.
- Dark and Troubled Past: The Marquess's Backstory is awfully sad and touching. In her life in the human world, her mother died when she was eight and she was abused by her alcoholic father. Then she stumbled into Fairyland, lived there for many years, fell in love and became a queen, and not by marriage, and became pregnant. And then she was snatched back into her dull world, all the ones she loved and who loved her in Fairyland gone, stuck with her abusive father and in a twelve year old's body, no husband, no child, nothing. Doesn't really surprise one that she became so bitter and full of hatred for Fairyland, first giving her so much love, and then taking it away again.
- Dude, Where's My Respect?: The whole reason for Mallow's FaceHeel Turn. When she returns to Fairyland, she finds that her kingdom has moved on and forgotten her.
- Fallen Hero: The Good Queen Mallow became the Marquess due to her anger at being returned to the mundane world. She still considers herself the hero.
- Faux Affably Evil: The Marquess can be all sweetness and light, but once you displease her she's going to hurt you.
- Freudian Excuse: A fairly dreadful one. As nasty as the Marquess is, you can't help but feel sorry for her. She was the daughter of an abusive tomato-farmer in Toronto who stumbled upon a doorway into Fairyland, then had adventures, conquered it, and became queen. Unfortunately, due to how Fairyland works, she couldn't stay and returned after a long life and rule to find herself back in her child's body, with nothing having changed in the real world. She spent her whole life trying to get back to Fairyland, only to find that it had moved on and forgotten her once she did.
- God Save Us From the Marquess: The Marquess has no problem killing her subjects, stealing their possessions, forcing them to wear iron chains around their wings (which, for the fey, is very painful) or splitting Fairyland forever from the human world).
- Jerkass Has a Point: many things that Marquess says are logical, including the fact that taking away one's father, is much worse than taking away one's spoon.
- Kaleidoscope Hair: The Marquess uses magic to change her hair color at will.
- Nice Hat: The Marquess has a very fine hat.
- Only Known by Their Nickname: The Marquess. Previously Mallow, the name Maud Elizabeth Smythe assumes in Fairyland.
- Sorceress Queen: Queen Mallow was quite the skilled magician, and as the Marquess she's just as powerful.
- That Man Is Dead: Mallow/Marquess. Though for a change, it is not entirely her fault. Rather the fairyland rules literally made Mallow disappear, though what happened afterwards is another story.
- 0% Approval Rating: Everyone is too afraid of her power to do anything.
September's shadow, who is removed in the first book then becomes the queen of Fairyland Below.
- Enemy Without: As a shadow, Halloween is Id personified. Specifically, the Id of September as she was on her first adventure, before she did some growing up. She has no self-control and freely indulges the darker, hidden whims September thinks better of doing.
- God Save Us from the Queen!: Played with. She does some cruel and terrifying things, and her non-shadow subjects are terrified that she'll send the Alleyman after them, but she is adored by her shadow subjects for giving them their own lives. The ending hints that with a way devised for the shadows and regular people to co-exist, Halloween can be a better ruler for everyone, and is left in power.
- HeelFace Turn: When it's demonstrated that the shadows and their other selves can in fact coexist peacefully, Halloween happily leaves off her more terrible, draconian policies.
- Jerkass Has a Point: While Halloween does many unsavory things (steals shadows from Fairyland Above, cuts shadows off of her own people, plans to force Fairyland Above to join the human world, etc), she does have a point when she argues that the shadows deserve to have their own lives, independent of the people they mirror.
- Love Makes You Evil: Halloween's ultimate goal was to merge Fairyland and the human world so she would not have to choose between her family and her friends.