Paci-Fire has the appearance of a demonic dark-grey baby with enormous black horns, a pink bull-like nose, glowing red eyes, and a black devil like tail. It also has a titular red pacifier being sucked by a second face on its torso. Paci-Fire also has a gold cross on its massive forehead with an eye similar to Bill's at its center and a red aura around its body. Of all the demons, it is the closest to traditional
Eons before the events of the series, Paci-Fire committed crimes before being called together by Bill Cipher, along with 8 Ball, Amorphous Shape, Hectorgon, Kryptos, Xanthar, Keyhole, Pyronica, and Teeth.
In "Weirdmageddon 3: Take Back The Falls," Paci-Fire says that it "butchered millions on countless moons" to Soos after he regarded Paci-Fire as cute.
In Weirdmageddon Part 1," Bill introduces Paci-Fire along with the rest of his demon friends to the residents of Gravity Falls. Afterwards, on Main Street, Paci-Fire and the other demons watch Bill turn Ford into a golden statue and taunt Dipper before burning the journals. Later on, Paci-Fire is seen drinking Time punch with Keyhole and enjoying the party Bill is having at the Fearamid until Time Baby and the Time Police invaded the Fearamid, but to the demons delight Bill vaporizes Time Baby and his squadron except Blendin. The party then continues as Paci-Fire and the other demons rejoice over Time Baby's presumed death.
In "Weirdmageddon 2: Escape From Reality," Paci-Fire and the rest of Bill's minions attempt to leave Gravity Falls and spread chaos across the world, but are stopped by an invisible barrier which makes Bill considers getting Ford 'out of retirement'.
In "Weirdmageddon 3: Take Back The Falls", he along with Bill's minions attacked the Shack-tron during the giant monster fight, during which he summoned a flock of giant Eye-Bats. But was defeated by the Shack-tron. He was sucked back to the nightmare realm following Bill's defeat along with the rest of the nightmares.