Heroes
Liana
- Voiced by: Kelly Sheridan, Melissa Lyons (singing voice)
One of the main protagonists, played by Barbie. Liana is a music-loving florist who lives in a cottage in the woods with her best friend Alexa.
- Childhood Friends: She and Alexa have been best friends since they were children.
- Fakin' MacGuffin: When Slyder attacks their cottage in search of Melody, Liana leaves behind a common mirror to trick the dragon while Melody's mirror is safely in Alexa's bag.
- Hair of Gold, Heart of Gold: She has blonde hair and is incredibly friendly and loving.
- Honorary Princess: She is proclaimed a Princess of Music alongside Alexa by the muses at the end of the film.
- Pink Means Feminine: Her peasant dress is pink, and her princess dress has mainly pink elements.
Alexa
- Voiced by: Cassidy Laden
The second protagonist of Diamond Castle, played by Teresa. Like her best friend Liana, Alexa is a music lover who helps run their garden.
- Brainwashed: After discarding her diamond necklace in a fit of rage, Slyder ambushes her and brings her to Lydia, who hypnotizes her with her music in order to find out where Liana and Melody are.
- Childhood Friends: Alexa and Liana have known each other since they were young children.
- Deadpan Snarker: She has her moments, particularly when dealing with Jeremy and Ian's antics.
- Graceful Ladies Like Purple: Her princess dress has significant shades of purple in it.
- Honorary Princess: She is proclaimed a Princess of Music alongside Liana by the muses at the end of the film.
- I Choose to Stay: Played with. During their quest to the Diamond Castle, Alexa opts to stay behind at the enchanted mansion in the woods rather than continue onwards, much to Liana's dismay and fury. This turns out to have been a trap set by Lydia, forcing Liana and Melody to rescue her. She also initially jumps at the chance to live in the Diamond Castle, but she quickly comes out of it and decides to return to her and Liana's cottage.
- True Blue Femininity: Her peasant dress is primarily blue.
Melody
- Voiced by: Maryke Hendriske, Lara Janine (singing voice)
A shy young woman who once served as the apprentice of the muses Dori and Phaedra. After Lydia turned against her fellow muses, Melody fled the scene and hid herself in a mirror, where she became trapped after Slyder broke her magic flute.
- The Apprentice: To Dori and Phaedra, at least before Lydia turned them to stone. Once they are freed, the muses promote Melody to the status of the third muse of the Diamond Castle.
- Forced to Watch: In order to draw Melody out of the mirror, Lydia forces a hypnotized Alexa to walk towards a cliff edge to her doom, and only Melody can ask Lydia to stop her.
- Living MacGuffin: Before the muses were turned to stone, they gave Melody the key to the Diamond Castle in case anything happened to them. Most of the plot revolves around Liana and Alexa protecting Melody from Lydia and trying to find the Diamond Castle before Lydia does.
- Meaningful Name: "Melody" comes from Greek origins, meaning "music" or "song". Quite fitting for the music-loving apprentice of two powerful muses.
- Red Is Heroic: She wears a red dress.
Jeremy and Ian
- Voiced by: Jeremy From (Jeremy), Noel Johansen (Ian)
A pair of identical twin brothers who befriend Liana and Alexa on their journey to the Diamond Castle.
- Always Identical Twins: Jeremy and Ian are identical twins and are nearly impossible to tell apart. In one scene, a woman at the tavern dumps water over Jeremy, thinking he was Ian (who'd upset her earlier).
- Identical Twin ID Tag: One of the few ways to tell the brothers apart is by the color of their vests; Jeremy's is red, and Ian's is green.
- Lounge Lizard: They regularly perform at inns and taverns, but are notorious for showing up late to their own shows.
- Twin Banter: They engage in this frequently with each other.Alexa: You're twins!
Ian: What? No! Really?
Jeremy: Mum should have told us. I feel cheated!
Ian: Duped!
Jeremy: Hoodwinked! - Ship Tease: Jeremy with Liana, and Ian with Alexa.
- Single-Minded Twins: The brothers often finish each other's sentences, particularly during moments of Twin Banter.
Dori and Phaedra
- Voiced by: Nicole Oliver (Dori), Heather Doerksen (Phaedra)
Two of the muses of music who guard the Diamond Castle and cultivate its songs. Once they were close companions of Lydia, but after the former muse turned against them, Dori and Phaedra were turned to stone and imprisoned in Lydia's lair.
- Graceful Ladies Like Purple: Phaedra wears a purple gown and is very graceful and poised.
- The Mentor: They served as this to Melody before they were turned to stone. Upon being revived, they reunite with Melody and elevate her to the status of the third muse of the Diamond Castle.
- Taken for Granite: They were turned into stone statues by Lydia after they tried to reason with her. Once Liana, Alexa, and Melody play their instruments, the muses are freed from their stone forms and reunite with their apprentice at the castle.
- True Blue Femininity: Dori wears a blue gown.
Villains
Lydia
- Voiced by: Kathleen Barr
Once a member of the three muses of music, Lydia is an egotistical sorceress who turned on her former friends in an attempt to rule the Diamond Castle herself. Now in possession of powerful hypnotic magic, she plans to hunt down Melody, who holds the key to the elusive Diamond Castle.
- Evil Costume Switch: Averted, as Lydia is wearing the same villainous outfit in her flashback as a muse. Played straight in the storybook version, where she's seen wearing a white Greek-inspired dress in the past.
- Evil Former Friend: Lydia used to be one of the three muses of the Diamond Castle along with Dori and Phaedra, and the three would cultivate the world's music together. But one day, Lydia became incredibly jealous of her friends and made clear her desire to be the one and only muse. When Dori and Phaedra disagreed and tried to reason with her, Lydia stormed out in a fury and vowed to take the Diamond Castle all for herself.
- Evil Redhead: She has bright red hair and is the main antagonist.
- It's All About Me: Lydia only cares about herself and her own desires, and doesn't care what she has to do to achieve her goals. In the past, Lydia was unsatisfied with being one of three muses and demanded to be made the one and only muse of the Diamond Castle, and turned on her former friends when her selfish desires were not met.
- Karmic Death: Lydia turned the muses to stone, and she ends up being turned to stone as well.
- Mind-Control Music: She uses her magic flute to hypnotize people into doing what she wants. She first uses it on the tavern owner to get him to say where Liana and Alexa went, and after realizing that it won't work on the girls while they wear their stones, she hypnotizes the owners of a mansion into giving their home to the girls and trying to stop their quest. When Liana and Alexa fight over this decision, Alexa rips off her necklace in anger, giving Lydia the opportunity to brainwash her.
- Nightmare Fetishist: Her extended villain song includes a line where she sings about how she loves dogs with rabies.
- Vain Sorceress: She wants to be the world's only muse so that people will worship her, and keeps the mirror that Slyder retrieved from the cottage to admire herself.
Slyder
- Voiced by: Mark Acheson
Lydia's dim-witted flying serpent and loyal minion. He has the strange ability to detect Melody's presence when she sings.
- Bumbling Sidekick: He's not very bright and is very easily duped by the protagonists. When he attacks Liana and Alexa's cottage in search of Melody, he picks up the wrong mirror, and accidentally sets fire to the cottage in the process.
- Sycophantic Servant: Slyder is intensely devoted to Lydia and frequently gushes about how amazing she is.
- Taken for Granite: He gets turned to stone along with his mistress at the end of the film.
