Teeth is a being shaped like a pair of dentures, with large white teeth and elongated pink gums as limbs with small hands and feet. Teeth also has a small pink aura.
Eons before the events of the series, Teeth indulged in criminal activities before being called together by Bill Cipher, along with 8 Ball, Amorphous Shape, Hectorgon, Keyhole, Kryptos, Paci-Fire, Pyronica, Lava Lamp Shaped Creature, and Xanthar.
In "The Last Mabelcorn", after Ford receives Bill's warning that Weirdmageddon is coming, Teeth is briefly seen on an image of a wheel with symbols.
In "Weirdmageddon Part 1", during the cold open, Bill introduces Teeth with the rest of his friends to the residents of Gravity Falls. Afterwards, on Main Street, Teeth and the other demons watch Bill turn Ford into a golden statue, taunt Dipper and burn the journals. He then tells Teeth and 8 Ball to eat Dipper as a reward. However, Dipper manages to get away from them. Later in the episode, after Time Baby and the Time Police are vaporized, Teeth and 8 Ball approach Bill to warn him that Dipper is still roaming free, and might try to free Mabel from her bubble. However, Bill isn't worried, as he has Gideon on the case, so the party carries on.
In "Weirdmageddon 2: Escape From Reality", Teeth 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. Teeth is seen missing one of its teeth after the collision, though it is later seen without missing teeth. Teeth and its comrades are then subjected to Bill's rage over the situation.
In "Weirdmageddon 3: Take Back The Falls", Teeth participated in the battle against the Shacktron. Following the monsters' defeat, it flees, screaming while on fire. After rounding up the townsfolk with its comrades, it eats Shmebulock in response to Grenda's claim that they would rather die than surrender. Following Bill's defeat, Teeth is sucked back to the Nightmare Realm along with the rest of the demons, vomiting Shmebulock back up in the process.