Mabel "Anti-Mabel" Pines is one of the alternate universe versions of Mabel Pines trapped in MAB-3L, the realm where the lost Mabels remain, and the main antagonist of the section "Don't Dimension It" from the Gravity Falls book "Gravity Falls: Lost Legends". She is an evil alternate version (a doppelgänger) of the main Mabel who plans to destroy the latter's realm by pretending to be her friend.
Anti-Mabel's appearance is almost identical to the main Mabel's appearance, which she used in order to fool the latter. The only difference is that Anti-Mabel wears a shirt that says "I HATE CATS" underneath her sweater, which was revealed after the main Mabel took of her sweater.
Anti-Mabel is initially shown to be almost identical to the main Mabel, but it is later revealed that she is the exact opposite of the main Mabel when she trapped the latter inside the outhouse.
At some point, Anti-Mabel was kicked out of her own dimension for being so evil. She eventually ended up being trapped in MAB-3L.
After some time in MAB-3L, she met Mabel Pines (the main Mabel), who was trapped there as well. She befriended the main Mabel and they teamed up together to send a signal for the main Mabel's grunkles, Stan and Ford, in order to save them. Since the signal was under the Military Expert Mabel's watch, they distracted her in order to steal the signal so that Stan and Ford will notice it and go there.
After this, the main Mabel went to the outhouse, but then Anti-Mabel revealed her true colors and locked her inside in order to prevent her from escaping. The main Mabel asked her what kind of Mabel she is, to which Anti-Mabel said that she is the exact kind of Mabel that the main Mabel is not. Before leaving, she explains her evil plan to the main Mabel. She then fools Stan and Ford into thinking they rescued the main Mabel. However, Ford realized that something is not okay with her. This was proved right when Anti-Mabel trapped them in the airlock.
Meanwhile, the main Mabel teamed up with the other alternate versions of Mabel in order to stop Anti-Mabel. Using their grappling hook, the Mabels went up in order to defeat Anti-Mabel. During the fight, Military Expert Mabel is injured, but the main Mabel encourages her to stay strong. Meanwhile, Flame Mabel and Threebel freed Stan and Ford from their cells, much to Ford's delight, who then says that the math saved him, like in his dreams.
Then, Anti-Mabel traps the other Mabels who rescued Stan and Ford using Ford's stolen Alien Adhesive gun. However, the main Mabel, using her grappling hook, knocked off her gun. Enraged, Anti-Mabel threatens to knock the glitter off her, to which the main Mabel taunts her that she would like to see her trying. Anti-Mabel then distracts the main Mabel when she says "Look! A puppy", and when Mabel says "Where?", she punches her.
Anti-Mabel and the main Mabel continue to fight, but Stan and Ford can't know which Mabel is their real niece. As Ford thinks of a way to distinguish between them, the main Mabel manages to take off Anti-Mabel's sweater, revealing a shirt saying "I HATE CATS" underneath her sweater. Since the main Mabel likes cats very much, Stan and Ford immediately knew who is their real niece after Anti-Mabel was exposed.
Anti-Mabel is then trapped in the airlock, and while she pounds, she furiously says to the main Mabel that in every selfish choice the latter makes, that being just like her, to which the main Mabel says that this is for Military Mabel. Then, Anti-Mabel is launched into the vacuum of inter-dimensional space, never to be seen again.
It is unclear if she survived this, but it can be assumed that she is still floating in the vacuum of the Multiverse or trapped in MAB-3L forever.
- As Anti-Mabel is an alternate version of Mabel, it can be assumed that also she was born on August 31, 1999.
- As the exact opposite of Mabel, if Mabel likes something, Anti-Mabel dislikes the mentioned thing.
- Mabel likes cats; Anti-Mabel dislikes cats.
- Mabel likes glitter; Anti-Mabel dislikes glitter.
- Mabel likes boys; Anti-Mabel dislikes boys.
- Mabel likes puppies; Anti-Mabel dislikes puppies.
- Anti-Mabel is the only known version of Mabel Pines who is the exact opposite of her rather than being similar to her, as all the other Mabels are similar to Mabel.
- She is the second villain from Gravity Falls to be a doppelgänger, the first being Dippy Fresh, who is the Mabeland version of Dipper Pines.