Meteora becomes the main antagonist of the latter half of season 18 when she rediscovers her true parentage and background and subsequently plots to take the throne of Fairy World from the Fairywinkle family. In "Divide and Conquer", she is reverted back to infancy following her defeat at the hands of her mother Eclipsa.
As the headmistress of St. Olga's Reform School For Wayward Princesses, Meteora, then known as Miss Heinous, had pale white skin and short, curly white hair with gray sides. She wore a purple Victorian era-style dress with black sleeves, light gray gloves, black earrings, and black high-heeled boots underneath her dress. She had a mole on her right cheek, and a long, pointed nose. Whenever she lost her poise, periwinkle blue club-like marks appeared on her cheeks. In "Heinous", she wears makeup to conceal said marks, her hair is messier, and her dress is tattered due to her currently being homeless. She also wore pale red lipstick and black mascara.
At the end of "Monster Bash", she gains several monster-like characteristics: yellow eyes, sharp teeth, pointy ears, and a scaly left arm. At the end of "Skooled!", she becomes even more monster-like: a slightly burlier physique, short black horns, slitted pupils with light yellow sclerae, reddish forearms and legs with dark red tiger stripes, and a thin red tail. Her thick white curly hair also grows longer, now reaching to her waist and eliminating the grey sides with her dress shredded up due to her monster transformation.
As of "Tough Love", Meteora has grown to considerable size and bears a close resemblance to her father Globgorwith her entire body becoming purple with darker purple stripes.
At the end of "Divide and Conquer", Meteora is reverted back to an infant. She has purple-magenta eyes with slitted pupils, a small patch of curly light purple-magenta hair, clawed fingers and toes, fairy wings, pale red-tipped ears, and a thin dark purple tail with a plume of light purple fur. She also no longer has a mole.
In "Gone Baby Gone", Meteora grows into a kid along with Marra, Poof, and Foop after spending ten years on Hekapoo's planet. Compared to her original teenage appearance in "Skooled!", this form sports an undercut hairstyle, has more monstrous features such as small black horns, a thin dark-purple tail, and more prominent pale red stripes on her reddish forearms and legs. Her attire consists of a brown leather tunic, bone earrings, and footwear with open heels and toes.
In her Ultimate Magic Form, she gains four extra arms, and her large, teardrop-shaped butterfly wings are lavender in color, trimmed in white, with undertones of purple in the shape of flowers with green seed-shaped designs in the edges.
When first introduced, Miss Heinous wants to strictly control bad behavior in wayward princesses, forcing them to act like "proper" princesses with no individuality of their own.
Toward the end of her debut episode, Miss Heinous struggles to contain her individuality once she loses control of her emotions, and club-shaped marks appear on her cheeks.
In her first appearance, she had a habit of second-guessing her choices of words, questioning whether they were appropriate for the situation.
In her third appearance, Miss Heinous has been shown to have become deeply unhinged, desiring gruesome vengeance against Timmy, and even wanting the entire multiverse to fear her. She also seems to have developed a motherly attachment to Rasticore, coddling his regenerating arm.
In "Fairy Bash", Miss Heinous starts to remember her original identity after seeing her old nursery and insists that Gemini refer to her as Meteora.
"Skooled!" shows that Meteora suffers from some abandonment issues, demonstrated from the way she reacts to Rasticore's attempt to quit his job as her bodyguard. This may be the result of her particular upbringing by the robotic headmistress St. Olga.
From "Tough Love" onward, Meteora becomes obsessed with reclaiming her birthright of the throne of Fairy World, being willing to crush anyone who tries to stop her. She has even grown more mentally unstable, becoming cruel and sadistic without a care of destroying the very kingdom she sought to reclaim.
Following her reversion into an infant, she acts in much the same way as any baby, save for still showing extreme hostility toward Timmy, such as leaving mutilated dolls of his likeness in his bed and hissing if she so much as hears his name. It is revealed in "Gone Baby Gone" that while Meteora doesn't remember her original memories, a part of her still hates Timmy (though she seems to finally be warming up to him after reverting back to an infant).
As the headmistress of St. Olga's Reform School for Wayward Princesses, Miss Heinous makes sure her staff has the princesses attending her reform school reformed into "normal" princesses. For particularly troublesome princesses, she uses the "Solitary Conform-ment Chamber", which forcibly brainwashes them into acting the way she wants them to.
In "Goblin Dogs", Pony Head reveals that Miss Heinous has left St. Olga's.
In "Gift of the Card", Miss Heinous is seen living with her assistant Gemini in a rundown apartment complex, with very little money. She hires Rasticore Chaosus Disastervaine to find and destroy Timmy's godfamily and bring Timmy to her as revenge for what they did to her. However, Rasticore fails, and his forearm is delivered back to Miss Heinous, to her displeasure.
In "Miss Heinous", she, along with Gemini and Rasticore's slowly regenerating arm, comes to the Turner Household, informing Timmy's parents that he has wronged her. After a brief negotiation, she is able to convince them to allow her to punish him by filming a video for the rebel princesses Timmy inspired where he renounces the words he used to incite the revolt. Despite Timmy saying this in a deeply sarcastic way, Heinous is satisfied with the results and departs. That night, as she prepares to sleep inside her car, she talks to Rasticore's arm, telling it she will annihilate Timmy and his godfamily, and make the multiverse "shiver in fear" of her. As she says this, she removes the makeup used to hide her cheek symbols.
In "Princess Turdina", Miss Heinous returns to the planet in an effort to get control back. She reveals to her former students that the "Princess Timmy" they idolize is a boy, and she also says she needs them just as much as they need her. However, the students chase her off once again, and she starts using princesses as fuel to restore her youth.
In "Fairy Bash", Miss Heinous tries to steal Timmy's youth, but ends up becoming part of a conflict between Timmy and Mina Loveberry, during which she is revealed to be Meteora Fairywinkle, the half-breed daughter of Queen Eclipsa and her monster lover Globgor. In "Eclipsa and Wanda" and "Fairy Trap", it is further revealed that she was replaced by the peasant girl Etheria as Eclipsa's daughter and heir after her mother was imprisoned, and all evidence of her existence was erased from royal records.
In "Skooled!", Meteora once again invades the planet, this time to discover what happened to her when she was a baby. After confronting and destroying her adoptive mother St. Olga, ripping off Pony Head's horn, tearing out Gemini's robotic heart and blowing up Rasticore's body, she sets out to reclaim the throne of Fairy World for herself.
In "Tough Love", Meteora goes on a destructive and soul-stealing rampage across Fairy World in her efforts to seize the Fairy World throne. Wanda and Eclipsa confront her and try to reason with her peacefully, but when that fails, she attacks Wanda, leaving Wanda in a vulnerable state, and flees.
In "Divide and Conquer", Meteora invades Fairywinkle-Cosma Castle in a mad attempt to seize control from acting king Timmy, eventually succeeding in stealing the souls of everyone on Fairy World except Glossaryck, Eclipsa, Timmy, and Tam Lucitor, who is somewhat immune to her soul stealing gaze due to having thousands of them. After a furious battle against Timmy, Meteora is defeated when her own mother Eclipsa uses the magic wand to revert her back to a baby.
Meteora briefly appears in "Escape from the Pie Folk". crawling around the room Timmy, Chloe, Janna, Mr. Pants, and Cosmo are staying. She gives Timmy an unnerving glare, leading Timmy to nervously wonder if she remembers anything from her former life.
Meteora appears to be teething in "Wanda Remembers" as a tooth/fang is shown in her mouth and Glossaryck comments at the rate her teeth are growing as she chews on him.
In "Surviving the Spiderbites", Janna attempts to feed Meteora, only for her to bat away the spoon and bite her hand.
In "Cornball!", Eclipsa brings Meteora to the fairy/monster cornball game, but Meteora keeps wandering off. At the end, she is seen watching the fairy and monster kids playing their own game and enjoying it.
In "Meteora's Lesson", Glossaryck takes Meteora back in time in order to help her learn to dip down. When they encounter a ten-year-old Toffee (who had broken Glossaryck's arm around that time), Meteora grows angry enough to succeed in dipping down and attacks Toffee. Glossaryck, satisfied with her success, returns them to their proper time.
She is briefly seen during "The Knight Shift", being taught shapes by her mother.
In "Cornonation", Meteora is present for her mother's queen coronation ceremony. When Globgor is revealed to have been released from his prison, suspicion falls on Eclipsa, and Hekapoo imprisons Meteora in a cage. When Globgor appears before the fairies and gets into a confrontation with the Magic High Commission, Meteora frees herself from her cage by dipping down, and seeing her helps Globgor calms down.
In "Gone Baby Gone", Meteora accidentally stumbles into Hekapoo's dimension with Poof, Foop, and Timmy's baby sister Marra, and they grow up into ten-year-olds with a close sisterly bond. When Star and Marco follow them to bring them home, they initially refuse and attempt to trade Star and Marco away to a demonic wish-granter in exchange for giving Marra magic powers. After the wish-granter is defeated, Poof, Foop, Meteora, and Marra agree to return to Earth when Timmy, Chloe, Janna, Mr. Pants, Brandon, Cosmo, and Wanda entice them with the offer of food, and they revert back to infants.
In "Ready, Aim, Fire", Meteora shows concern for her father after he is wounded by a Solarian blade.
In "Cleaved", Meteora helps Timmy, Cosmo, Wanda, Poof, and Eclipsa destroy all magic in the universe. After her family is reunited once more, Eclipsa decides to enroll Meteora in kindergarten.