Jazz Fenton

Jasmine "Jazz" Fenton is the eldest, and more intellectual child of Jack and Maddie Fenton, and the big sister of Danny Fenton.

History
Danny may have the superpowers in his family, but Jazz has the brains and social skills. She starts off the show as the intelligent older sibling who believes her parents' "sick obsession" with ghosts is silly. She is often overprotective of her brother Danny to the point of annoyance and views herself as the most normal member of the family. As a result, and as depicted by heavily detailed journals Jazz has kept for years, she also used to be self-righteous.

Jazz eventually accepts that ghosts are real when, unknown to Danny, she watches him transform. At first, Jazz tries to question Danny's best friends, Sam and Tucker, but she quickly gives up once she realizes that they won't betray Danny's secret. When Danny rescues her the next day while in ghost form, Jazz pretends to be scared of him and runs away. Smiling, she tells herself that "he can tell me when he's ready."[5] As a result, Danny has no clue that she now continuously covers for him when he's out fighting ghosts.

Jazz gradually changes in her views of ghost hunting when she is forced to accompany her father in barricading their own home to protect it from a massive ghost invasion sent by Vlad Masters to murder Jack. In spite of her assurance to her dad that ghost hunting is nothing but a social experiment, she finds herself enjoying it, easily adapting to the Fenton equipment. Ever trying to be mature, Jazz eventually embraces her childhood, proving that she doesn't need to be the adult all the time and ultimately creating a balance between the two.

While Danny is reworking a desolate timeline so he won't become Dark Danny, Jazz sends him a note ten years in the future to inform him about Vlad. With this, Danny not only finds out about Vlad, but also that Jazz knows about his double life. After defeating Dark Danny, Jazz confesses to Danny that she's known his secret for a long time and was only waiting until she thought he was ready to tell her. Danny and Jazz, in a touching moment, embrace, finally able to reconnect.

Jazz begins to try and take a more active role in Danny's ghost fighting, and although she means well, her inexperience results in more than a few embarrassing defeats for Danny, such as accidentally sucking him into the Fenton Thermos multiple times. Danny loses his temper with her about her unnecessary help and the fact that she always makes things worse. To prove Danny wrong, Jazz ventures to the home of Vlad Masters in hopes of helping Danny out, but ends up forced into combat with Danny. They come up with a plan to work together to defeat Plasmius. Afterward, the two smooth out their conflict and Jazz reverts back to her old method of covering up for him and only helping when she's needed. In gratitude, Danny dubs her a member of Team Phantom, a role she plays more fully much later when she teams up with Maddie and Sam to defeat Spectra, Ember, and Kitty when they overtake Amity Park and make all the men disappear.

With her new-found love of ghost hunting, she expresses it as part of her social life, even going so far as writing her college entrance thesis on "ghost envy." At the end of the series, Jazz reveals the truth about Danny's ghost powers to their parents when she thinks he's been killed in a crash. Later, when he turns up in one piece, she explains to Danny that she told their parents about his secret.

Appearance
Jazz, like her brother, Danny, has a similar facial structure and appearance to her mother, Maddie. She is a young teenage girl with aqua blue eyes, like her father, Jack's, and long auburn hair, like her mother's, which reaches down to her hips. She wears an aqua headband, a black long-sleeve v-neck shirt, aqua pants, and a pair of simple, black flats. Other than wearing a black tank top in one episode, the Fenton Peeler, and two different Ember costumes, she is one of the characters who has the fewest costume changes.

Personality
Jazz, being the oldest sibling and insisting that she is the most rational member of her family, takes it upon herself to be the "mature" adult, often criticizing her parents' obsession with ghosts and being overprotective of her little brother. She believes she is an adult stuck in a teenager's body and wants to be a good role model for her younger sibling, and is often concerned about his development and well-being, much to his annoyance.

While she may not consciously know it, she tends to think that her intelligence makes her superior to others and can go completely bonkers if she's shown to be wrong. She often uses her older-sister status to boss Danny around, acting more like a mother than a sister, but ultimately, she means well, and tries to use her knowledge and her understanding of psychology to point her parents in a more "normal" direction, even if it sometimes is quite annoying to others.

Although she is an adult stuck in a teenage body, she does have one weakness: Bearbert Einstein, her favorite stuffed teddy bear. In "The Fenton Menace," when Danny Fenton tears the little bear apart, Jazz throws a fit, jumping up and down while crying. This makes her realize that she doesn't have to be the adult all the time and that there's nothing wrong with being a kid sometimes.

Jazz gradually develops as the show progresses, starting off as a rather snobbish genius who refuses to be associated with her parents, only to later embrace the family ghost-hunting trade. Her sudden increased interest in ghosts causes Jazz to believe that she is suffering from "ghost envy," stating she desires to be a ghost if only to get her parents' attention. In addition, she develops a deep respect for her brother's selflessly heroic nature and supports him through thick and thin.

At school she is apparently popular and very social. She is one of Casper High's best students according to Mr. Lancer and gave a school spirit speech that was applauded and cheered on by everyone in attendance.

Danny Fenton
When Jazz and Danny were younger, they used to talk all the time and were quite close. But as Danny says, that came to an end when she turned into "a fink." Becoming snobbish, bossy, annoying, overprotective, and too mature and smart for her own good, Danny felt he could no longer talk with her no matter how much she tries to bond with him, and as a result their relationship became strained. She unintentionally treats him like a helpless child that needs guidance and direction until she secretly witnesses him transform into his ghostly alter ego. Realizing that he is a hero of sorts and can take care of himself, and although she never truly stops worrying about him, she stops seeing him as a helpless baby brother and is able to respect him as the young man that he is. This allows their bond to strengthen and they both look out for one another, with Jazz finally realizing Danny is more responsible and mature than she thought.

Jack and Maddie Fenton
In the beginning of the show, Jazz tends to clash with her parents often because she disapproves of their ghost obsession. She feels that they don't provide the proper guidance that she thinks her younger brother needs. But when she steps into their ghost-fighting shoes, she begins to understand them better, eventually gaining a ghost-hunting obsession similar to her parents. This allows her respect for them to grow, although she still criticizes them for going overboard on the ghost fighting. Jack has even admitted that Jazz is his favorite even though she looks nothing like him, and it's hinted that Jazz's name was his idea. In "Phantom Planet," Jazz believes Danny was killed in a crash. Distraught, she explains to her parents that their son is really the ghost boy, helping them to accept his shocking secret.

Sam Manson and Tucker Foley
Although Jazz is never seen with friends of her own age, she has been known to hang out with Danny's friends. She hangs out with them more often when she becomes a member of Team Phantom. Sam is at first critical of Jazz, but later warms up to her in "Girls' Night Out." Her relationship with Tucker isn't explored as much, but it is clear she thinks of him as a friend.

Johnny 13
Johnny 13 rescues Jazz from a runaway roller coaster that he secretly sent flying. Johnny's girlfriend Kitty needs a host to overshadow in order to exit the Ghost Zone, and Johnny chooses Jazz to be his girlfriend's new body. Goody-two-shoes model student Jazz seems to be attracted to Johnny's bad-boy image, not to mention that he saved her life, and begins to date him despite her parents' and brother's strong disapproval. Kitty transferred her energy into her scarf, jacket, and ring, meaning that if Jazz wears all three items, Kitty will be able to possess her. Johnny does his best to win Jazz over and persuade her to wear Kitty's things, and succeeds for a minute or so until Danny rescues Jazz from the items' influence and throws Johnny back into the Ghost Zone.

Although Jazz is definitely grateful to Johnny for saving her life, it's unclear how much she really liked Johnny since for the majority of their relationship she was under Kitty's influence.

Vlad Masters
Before she finds out about Vlad's ghost powers, Jazz seems to respect him or is at least courteous to him. But after it's revealed to her that Vlad is her brother's archenemy, Jazz distrusts him and is wary of him being around, as she now knows how dangerous he can be. Vlad's love for Maddie creeps Jazz out.

Dark Danny
As Danny plans to cheat on the C.A.T., Jazz meets Dan, the evil Danny Phantom from the future. He reveals his true self to her after she admits that she knows his secret identity–much to his surprise–but he knocks her unconscious twice during their run-in anyway. Once she realizes he's not the Danny she knows and loves, she sends the younger Danny helpful information and reveals Dan's treachery to everyone at the Nasty Burger.

Freakshow
Jazz seems to have a small connection with him because they both have ghost envy, going as far as wishing they both were ghosts. But thanks to that connection, she's able to give Danny advice about how to defeat Freakshow later on.

Intellect
Jazz is downright one of the smartest characters in the series, getting the highest score in the C.A.T. She hopes to either be a brain surgeon when she graduates college or a professor at Yale. She also shows interest in psychology, shown when she tries to get a rebellious, intimidating student, Spike, to open up to his parents and tell them how he feels and whenever she believes she knows what Danny wants or what he's going through.

Master Strategist
Being very smart, she is a cunning strategist, and brings a new dimension to Team Phantom that can save them at the most unexpected times. Her strategy skills are useful when she goes undercover to seek out Vlad's secrets in his castle or manipulates Freakshow to figure out his weakness to helps Danny defeat him. She's the one who concocts the plan to capture the three girl-power ghosts and reverse their effects on the town.

Combat Skills
At a very young age she has shown to be prominent fighter, especially when it comes to protecting her brother. She has also proven to be a skilled ghost hunter, just like the rest of her family. One time, she defeated a swarm of ghost animals with her father with relative ease and even pleasure.

Daily Exercise
Jazz's physical ability is an important part of her life and keeping up with her brother. She says she usually does cardio, as it is a major factor in her personal upkeep. When fighting, she has to be able to endure hits and return blows with ease, though she does it mostly to keep herself healthy.

Transportation
She uses a car of her own and sometimes drives the Fenton RV and the Specter Speeder.

Trivia

 * She is a bad singer, as shown in "Girls' Night Out."
 * She keeps a toy bear named Bearbert Einstein.
 * In "Attack of the Killer Garage Sale," Dash has an unrequited crush on Jazz and invited her to one of his parties, which she didn't go to.
 * In one of Butch's live streams, Butch Hartman stated that if Jazz fought Vicky in a boxing match, Jazz would win due to her extensive knowledge. In a street fight, however, Vicky would beat Jazz due to sheer power.
 * She was the fourth person to know about Danny's ghost powers, after Sam, Tucker, and Vlad.
 * In one of Butch Hartman's videos, he stated that Jazz's color scheme comes from combining both Maddie and Jack's color schemes.
 * Jazz is the only member of Team Phantom that has yet to meet Danielle, which is ironic considering that they are genetic siblings.
 * Jazz seems to have inherited her prowess for the martial arts from her mother.