Eons before the events of the series Pyronica indulged in criminal activities before being recruited by Bill Cipher, along with 8 Ball, Amorphous Shape, Hectorgon, Keyhole, Kryptos, Pacifier, Teeth, and Xanthar.
In "The Last Mabelcorn," the arrival of Pyronica along with her demon comrades into Gravity Falls' dimension is foreshadowed in Ford's flashback of him working with Bill. When Bill mockingly tells Ford that he has betrayed him, Pyronica's laughing silhouette is seen in the representation of another dimension projected in the Mindscape.
In "Weirdmageddon Part 1," during the cold open, Bill introduces Pyronica with the rest of her demon friends to the residents of Gravity Falls. Afterwards, on Main Street, Pyronica and the other demons watch Bill turn Ford into a golden statue and taunt Dipper before burning the journals. Later in the episode, Pyronica is seen playing "Spin the Person" at the "V.I.P." party Bill is having at the Fearamid. When the calcified statue of Lazy Susan points in Hectorgon's direction Pyronica happily swallows the demon whole.
In "Weirdmageddon 2: Escape From Reality," Pyronica and the rest of Bill's friends attempt to leave Gravity Falls to spread their chaos across the world, only to collide with an invisible barrier.
Pyronica is a pink glowing demon with short pink hair, bangs parted across her face, and several small horns across her skull, in between her two other big curved horns. Pyronica has one eye, just above her wide mouth and thick lips, that hide her buck teeth and fangs. Pyronica has a slim humanoid body, and her limbs are made of white flames. Pyronica wears a long pink cape and pink stiletto pumps.
- 215. "The Last Mabelcorn" (flashback, no lines)
- 218. "Weirdmageddon Part 1"
- 219. "Weirdmageddon 2: Escape From Reality" (no lines)
- 220. "Weirdmageddon 3: Take Back The Falls"
"Spin the person! Spin the person!"
- Pyronica is the personification of Bill's blue flames.
- Early concept art of Pyronica shows that is was initially going to have snake-like hairs with mouths on the edges, a longer cap, very long hair, bigger and sharper horns, and limbs made of red fire.
- In a closer final revision of Pyronica, the demon's limbs were to be made of blue flames instead of white.
- Pyronica's name is a pun on the Latin word for fire, Pyro, and the name, Veronica.
- Pyronica has appeared in 4 episodes, more than any other demon.
- Pyronica also has 3 quotes, more than the other demons.
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