Eons before the events of the series, Keyhole indulged in criminal activities before being called together by Bill Cipher, along with Lava lamp shaped creature, 8 Ball, Amorphous Shape, Hectorgon, Kryptos, Teeth, Paci-Fire, Pyronica, and Zanthar.
Keyhole, first appears in "The Last Mabelcorn", near the end of the episode, in a flashback, when Ford confronts Bill for lying to him, Keyhole'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 Keyhole with the rest of his friends to the residents of Gravity Falls. Afterwards, on Main Street, Keyhole and the others watch Bill turn Ford into a golden statue and taunt Dipper before burning the journals. Later in the episode, Keyhole is seen drinking Time Punch with Paci-Fire and enjoying the "V.I.P." party Bill is having at the Fearamid until Time Baby and the Time Police crash the party. To the beings's delight, Bill vaporizes Time Baby and his squadron. The party then continues as Keyhole and the others rejoice over Time Baby's presumed death.
In "Weirdmageddon 2: Escape From Reality," Keyhole, first appears partying along the rest of the Henchmaniacs, later he listens to Bill's plan to expand his chaos worldwide and later, he and the rest of Bill's minions attempt to leave Gravity Falls and spread their chaos across the world, but are stopped by an invisible barrier around the town. A short time afterwards, Keyhole is not seem with any visible injuries, meaning that maybe crashing againist the barrier wasn't that painful for him, still, he's subjected towards Bill's anger towards their inhability to escape and attacks them, with lightning bolts, Keyhole barely, manages to dodge a lightning bolt that almost hits him. Later Keyhole informs Bill that Gideon allowed Dipper, Wendy and Soos to enter Mabel's bubble. Bill is unconcerned, believing that no-one can escape the bubble's temptations, and tells Keyhole to bring him Gideon and take the rest of the day off.
In "Weirdmageddon 3: Take Back The Falls," Keyhole, first appears in an imagination that Bill has in which he attempts to convince Ford to make a deal with him, in which his minion appear destroying planets with him, in there Keyhole, appears playing tennis with Kryptos, using a planet as a ball. Later, he witnesses Bill torturing Ford and laughs at him, later, when the Shacktron, punches a hole through the Fearamid, he's taken back, after seeing that exist people that actually survived Weirdmageddon and attempt to fight back at Bill. So Bill forces him and his minions to fight aganist the Shacktron and changes to a "darker form" and jumps from the Fearamid to fight. Later, before the fight starts he's accidentally hurt by Soos, along Paci-Fire and Pyronica, when his microphone causes a feedback and they cover their ears, later, when the fight actually begins, he participates in the battle against the Shacktron and charges towards it, along his comrades, when Mabel uses the Shacktron cannon to attack, Keyhole, decides to flee from the battlefield. Following Bill's defeat at the hands of Stan, he was sucked back to the Nightmare Realm along with its fellow nightmares. He's the 4th Henchmaniac in being sucked by the rift.
Keyhole has a aqua humanoid body and a large forehead with a few orange spots on the side and a large hole resembles a keyhole. Keyhole has a darker shade of blue around its eyes, a small pink nose and small blue aura.
- Intro: "Gravity Falls Main Title Theme"
- 218. "Weirdmageddon Part 1" (no lines)
- 219. "Weirdmageddon 2: Escape From Reality"
- 220. "Weirdmageddon 3: Take Back The Falls" (no lines)
- In concept art, Keyhole was going to have green skin.
- Keyhole is the smallest of the Henchmaniacs.
- He has been seen with and without the darker shade of blue around his eyes.
- Keyhole, along 8 Ball make a cameo in Gravity Falls: Lost Legends, during the tale "Don't Dimention It!", while Mabel is falling through dimentions, they're standing next to a statue of Bill Cipher that has the label: "He was the wrost".
- This implies that Keyhole and possibly, that none of the Henchmaniacs actually liked Bill.
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