In most fan art, Mabel is described as very attractive and desirable. She usually wears no make up.
She is depicted as having very long, wavy, silky hair that reaches to her hips or knees. She also has blue eyes, which are completely different to the original Mabel's.Just as Dipper, Mabel is usually seen in blue and black. Her performance outfit consists of a solid black leotard, covered by a light blue jacket, with a black bow on the chest. She wears a pair of fishnet tights and a pair of blue or black, high-heeled shoes. Whenever she's not performing, she is usually depicted in either a blue jacket with a black shirt, a blue blouse with a black/blue skirt, or a black collared dress with a wide, bright blue panel down the front with the sleeve cuffs in the same shade. However, like her brother, she always wears her amulet, hers being in the form of a headband decoration.
In some interpretations of her, she's seen with a tremendously fat blue cigar in her mouth, which supposedly has multiple magical powers.
Unlike her Gravity Falls counterpart, Mabel Gleeful is known for being mean and deceitful to almost everyone in town. Many of the boys in the town have feelings for her, though they are solely based on looks, and are never returned.Like Dipper, she is obsessed with magic and lusts for power. She similarly enjoys torturing people, but she is more amused from the pain of her victims. Often, she laughs at her prey's misery, which sometimes leads to her brother's annoyance. Usually, these unfortunate victims are volunteers in their show, for which she is Dipper's assistant. In some headcanons, the twins are somewhat like their Gravity Falls counterparts, so Dipper is more cold and emotionless than Mabel, who is more vivid in her emotions, but this headcanon is not common. Dipper is also more serious, which is why he gets annoyed by his sister killing for fun.
Dipper is Mabel's twin brother and partner in crime, whom she probably 'cares' the most for. At the very least, she respects him and his powers. She enjoys spending time with him, whether it's torturing Will and their victims, or simply sitting at home and discussing their performance with him. She does love Dipper as a brother and partner. In some versions she and Dipper have a incestuous relationship.
She doesn't like it when he talks to Pacifica; it's unknown if it's because Mabel's jealous that Pacifica will steal Dipper from her, or she simply finds Pacifica too annoying for Dipper.
However, when they are torturing their victims, Mabel gets annoyed when Dipper is telling her to stay on task and calls him a 'killjoy', which Dipper hates. However, there are times when Mabel believes her brother to be a 'psycho' and too much for her. Despite this, she has never completely retaliated against him; whether this is from actual sibling love, or from doubt in her ability to defeat him, is unknown.
It has also been shown that Dipper's power and sinister amusement has made Mabel somewhat fearful before.
Unlike her brother, Mabel becomes amused by Gideon, (probably due to his futile attempts to be brave in front of her brother) and even tongue-twists him into a date with her. From then on, Mabel continues keeping in touch with Gideon. However, over time, Mabel starts to become suspicious and views him as a threat to her and Dipper's plans.
Mabel constantly teases Pacifica Southeast, but Pacifica still tries to show kindness to her. However, this doesn't stop Mabel. Later on, she begins seeing her as a threat, as Pacifica begins to hold influence over Dipper, which causes Mabel to start to hate her. In reality, she is jealous of Pacifica's life and personality, but Mabel never really admitted that.
While Dipper enjoys torturing Will, Mabel appears to feel some kind of pity for him, knowing that he also has a crazy brother (often, Bill and Will are related).
She still tortures him with Dipper, but most of the time, she does care about him, even having a somewhat friendly relationship.
(When Mabel caught Gideon trying to investigate the Tent of Telepathy.)
Mabel: "You know if you wanted to sneak backstage...you could have just said please."
Gideon: "M-mabel? How did you-?"
Mabel: "You didn't think my brother-dear and I would leave our treasures unguarded did you? *giggles* Remember how a 'magician never reveals her secrets'? Now what to do with you?"
(After tormenting a victim with Dipper.)
Dipper: "We have a show tomorrow, and I highly doubt the audience would be pleased with your blood covered blouse."
Mabel: "Relax brother, it's just a few droplets; nothing a small incantation cannot solve. Besides his screaming prayers for mercy were worth every drop."
Dipper: "And they almost costed us our test-subject for the night. Little good can come out of a blood spell if the blood isn't fresh from a live subject Mabel!"
Mabel: "And tonight was a win-win! You've got a subject for the next step...and I got to have a little more fun. So quit being such a-"
Dipper: "Don't say it!"