|Jafar says: Read my lips and come to grips with the reality!|
The Horrifying Sweaty One-Armed Monstrosity is a minor antagonist in the first part of the Gravity Falls series finale "Weirdmageddon".
He was a gigantic human head-like monster with drops of sweat around his face and reddest brown hairs and eyebrows with a large arm on the top of his head.
While his origins remain a mystery, the Monstrosity is first seen during the third day of the event called Weirdmageddon, when Dipper is looking for both his sister and Uncle Stan and thinks they're hiding in the town mall, the One-Armed Monstrosity passes by, as Dipper quickly runs towards the mall as fast as he could, however the Monstrosity notices him and asks if he'll go inside his mouth, as he gets closer, Dipper barely makes it through the doors in time as the Monstrosity tries to get him.
While Dipper and Wendy were on the road running from Li'l Gideon's henchmen, they nearly get caught by the Monstrosity's arm, he then grabs one of the prisoners then eats him and the entire car too.
He was last seen during the credits where he was still asking if anyone wanted to go inside his mouth, then talks to an off-screen woman only to hear her scream and run away, then sees a bird which he mistakes for a man, the Monstrosity doesn't care anymore then decides to leave and call his mother.
Later, he was sucked back into the Nightmare Realm during Bill Cipher's defeat.
- Louis C.K. improvised most of the Horrifying Sweaty One-Armed Monstrosity's lines during the end credits scene of "Weirdmageddon Part 1", including the "I gotta call my mother" line.
- After Louis C.K. was accused of five sexual assaults as part of the #MeToo movement in late 2017, Disney had series creator Alex Hirsch redub all the Horrifying Sweaty One-Armed Monstrosity's lines.