In this capricious tale of friendship, Jojo and Fat Louis meet a new classmate, a big-nosed girl named Violet Snout, as the school year begins. While the boys and the other classmates initially mock her for her nose, she unusually becomes a popular student to Jojo's surprise. But once the principal catches Violet for a scheme that helped her befriend the other classmates, not to mention Violet's mother hospitalized, the girl disappears from school. Jojo and Fat Louis set out to find her on the snowy night of Christmas Eve.
Its English dub can be found as an audio track on some DVD releases.
Jojo: The Violet Mystery provides examples of:
- Adaptation Amalgamation: According to this review in French
, the special's plot is derived from three Jojo volumes: Le Mystère Violaine, La Fugue de Jojo and Le Serment d'Amitié. - Big Eater: Mr. Cupcake makes a plethora of cakes on Christmas Eve for his son to consume. The young trio secretly eat the cakes in the boys' hideout near the ending, as an indicator to Jojo's grandmother and Mr. Cupcake that the boys have returned from their absences.
- Break the Cutie: Happens to Violet. Her new classmates tease her nose and shout "oink" at her, and she retaliates once by kicking a boy. She deceivingly gains acceptance from her classmates by stealing late passes from the principal's office until her punishment, in which she's stripped of her winning "queen" title in the school's Christmas costume party. Aside with her loving mother sent to the hospital, Violet flees "for good." After wondering solo and doing a "farewell" visit to her home, she reunites with the boys at the frozen lake, disappointingly followed by Fat Louis blaming her for missing his father's baked goods and risking their safety. Both boys tease at a defensive Violet and initially abandon her, leaving her to conclude that everyone hates her.
- Bully Hunter: When Slugger the bully threatens Fat Louis, Jojo bravely tackles Slugger to save his friend and preserve their friendship oath. Jojo is hailed a hero by the other kids.
- Collector of the Strange: Fat Louis keeps a collection of stems from the cherries he ate, a hobby Jojo despises in comparison to his painting.
- Crash-Into Hello: Jojo and Violet bump into each other at their first encounter. They eventually display signs of attraction.
- Danger — Thin Ice: Jojo and Fat Louis come across a frozen lake on their quest. The latter is fearful of the lake's surface breaking, yet Jojo throws a rock to successfully prove him wrong regarding the ice's durability. They find Violet at this location, but their following bitter argument results in the boys leaving her behind. When Violet walks away in despair, she slips and falls to the frozen lake to her apparent drowning. The boys attempt rescuing her from the lake and give up, but they immediately spot her aside and learn that a rock actually punctured the surface.
- Dean Bitterman: The principal is a no-fun and strict administrator who is assisted by Ms. Clover, who doesn't advocate harsh punishments to the students.
- Disappeared Dad: Violet's absent father apparently lives in distant Australia and is so wealthy he doesn't a have job. Except Violet always lived with her mother and never had a father in the land down under, leaving her father's actual whereabouts unclear to the viewer.
- Disney Death: After Violet drops to the frozen lake, the boys look back and spot a hole in the icy surface, and they try to save her from drowning with a stick. When the boys mourn, it's revealed that Violet is standing on the snow and didn't go to the water, instead it's a big rock that punctured the ice.
- The Faceless: The faces of Violet's parents are never seen. They're even obscured by shade in a fantasy sequence where Violet lives in Australia. This is averted with her aunt.
- Going in Circles: Near the suspension bridge in the forest they had traversed on, Fat Louis remarks that he and Jojo were going around in circles during their search for Violet.
- Good Angel, Bad Angel: Violet has these communicating to her during her dilemmas. Her devil recommends misbehavior such as comeuppances against the kids who make fun of her, while her angel encourages friendship with them. After being punished for stealing her classmates' late passes, she angrily banishes them and they stop reappearing.
- In-Series Nickname: Jojo and Fat Louis are respectively nicknamed "Bill" and "Eagle Feather" by each other, in homage to a story of a cowboy and Indian friendship shared by Jojo's grandmother. After becoming friends with the boys, Violet is ceremoniously given the nickname "Snowflake".
- Jerk with a Heart of Gold: Jojo displays shades of this as he quarrels or makes fun of his beloved friend Fat Louis.
- Upon reuniting with Violet, both boys return to ridiculing her nose during a dispute at the frozen lake and leave her behind in the cold night. Once the boys hear her scream and plunge to the frozen lake, they attempt to rescue her and subsequently mourn, admitting that they like her. Except she never entered the water and drowned.
- Land Downunder: In the schoolyard, Violet discloses to her classmates of having a very wealthy father who lives in Australia. Later, when she spots the same freight train ridden by Jojo and Fat Louis while they're searching for her, she hopes the train can transport her to Australia. She even dreams of going to school there with girls who look identical to her. The fact she has a father in Australia is bogus.
- Laser-Guided Karma: Jojo warns Fat Louis in their friendship pact that the one who breaks the oath will be immediately struck by lightning. Later, once Jojo denounces their friendship because Fat Louis didn't reveal Violet's scheme to him, Fat Louis frighteningly walks backwards and bumps a tree whose snow drops on him. Nevertheless, the boys chuckle and remain friends.
- Meaningful Name: Big-nosed Violet's surname is Snout.
- Nightmare Sequence: When Violet sleeps in the old woman's house, she dreams of the woman looming over her and making an Evil Laugh with her mouth stretching.
- Pie-Eyed: Some characters' eyes, usually Fat Louis', may appear like this.
- Racing the Train: When Jojo is inside an open train wagon, the train begins moving as Fat Louis is still outside. He chases the train wagon and grabs Jojo's hand to join him.
- Running Gag: The principal enjoys keeping his desk neat, although his supplies are repeatedly spilled or pushed by accident.
- Santa Claus: During their search for Violet, Jojo and Fat Louis come across a man dressed as Santa riding on a sleigh pulled by a horse. He gives the boys a ride across downtown before he picks up toys from a department store. Later, he transports the boys and Violet to the house before his sleigh flies to the sky.
- Senior Creep: After Violet rescues a meowing kitten from being stranded in a barrel, the cat's owner, who is an elderly woman, arrives to thank her. Violet asks her if she's a witch, the woman responding with a sinister-sounding cackle. Taking refuge in the woman's house, Violet leaves after a Nightmare Sequence revolving the woman and realizing that she will get turned in. When Violet returns to the city, the woman's shadow pops up and frightens her again, prior to the woman last seen talking to the police.
- Sworn Brothers: Jojo and Fat Louis' friendship oath binds them vigorously ever since it's sealed by each boy spitting between his fingers. The former likens themselves to brothers at one point.
- Two Guys and a Girl: Jojo, Fat Louis and Violet, especially once they're all friends to each other in the ending.
- Writing Lines: The principal orders Violet, who was late to school, to write in her notebook "I must not be late again" a hundred times.
