Chamelius is a pigmentologist and likes to collect colors from other dimensions and universes. He steals the colors with help from magic books he calls ''Hue-Collecting Tomes.'' He has sent many across the universes.
One of his Tomes ends up on the cemetery of Gravity Falls and was found by Dipper when he was doing one of his daily cemetery checks. Dipper brought the tome with him to the Mystery Shack. When he opened it, Chamelius used magical black ink to attempt to absorb Dipper's colors and the colors of his surroundings, but accidentally grabbed Dipper himself and pulled him into the book instead of the colors.
When Mabel finds the Tome on Dipper's bed, she starts to draw doodles in the book until she sees Dipper on the pages. While Dipper starts to explain what happened to him to Mabel, Chamelius appears as well and explains to the twins who he is and that he is a pigmentologist who collects colors. He wants to release Dipper but then hesitates when he realizes he can use Dipper's imprisonment in the book to get the twins to help him achieve his goal to collect colors. He convinces them to help him. If they make drawings in the Tome and Mabel colors them with all the colors she has, he will show them an unknown new color from the other universe and he will set Dipper free. The twins start working on drawings and coloring the book, much to Chamelius' pleasure.
After a couple of drawings later, he asks Mabel to stop with drawing princesses and superheroes because he already has thousands of books with them and doesn't need another. Dipper encourages Mabel to ignore Chamelius and just keep drawing what she wants to draw. When the twins learn that Dipper can draw too, even while stuck in the book, they continue together. Mabel keeps her promise and doesn’t forget to color her drawings in.
When Mabel starts to put mismatching colors together, the books start shaking and leaking ink. Chamelius pops up, angered, and accuses Mabel of making the bad color combinations on purpose to damage his book. Mabel apologizes and he allows her to continue.
After a while, Mabel notices that the more color she adds to Chamelius's book, the grayer her world looks. Chamelius lies to her that her eyes are just tired from looking at so many colors and demand her to keep coloring. But a little while later Mabel starts to realize that Chamelius has tricked her and Dipper. She warns her brother about Chamelius. They realize he is stealing all the color from their world every time they use a color for their drawings. Chamelius denies it at first.
When Mabel touches a paper of the book, she burns her hand on the page and the color of her skin shows up in the book. Dipper is angered at Chamelius for tricking him and hurting his sister and now threatens that he will hurt him for this. A panicked Chamelius sends out his black magic ink to grab and pull Mabel in the book as he did with Dipper. Dipper warns Mabel just in time and she can rip out the page before Chamelius can get a hold of her.
The twins then defeat Chamelius by drawing ugly drawings and color everything with clashing and mismaking colors. Chamelius is getting sick of it and after a final blow, his book explodes releasing all colors back into the world.
Dipper and Mabel mock him with his own book after these events. Mabel is only disappointed that she never sees the unknown color from the other universe. Chamelius makes a final offer to the twins. He will show them the color if they promise never to color in his book again and leave him alone. They agree and he shows them the color Shmerulean.
The twins are disappointed because they know the color. It's a glittery blue and Mabel has a nail polish in the exact same color. The twins leave Chamelius alone and decide to cover Stan's yellow toenails with the nail polish while he's asleep. Meanwhile, Chamelius wails because he will never see the color yellow again.
Chamelius appears as a chameleon who stands up on his back feet. He wears a long dressing gown with a round symbolic necklace. He has sharp, pointy teeth and three long fingers with long nails.
Because he appears in a book and comes from a universe where everything is black and white. His own colors don't appear and are unknown.
- Chamelius is obsessed with Soos. He calls him a good boy and occasionally asks the twins to make a drawing of Soos.
- Chamelius gets sick from clashing colors.
- He is amazed by the fact that humans can have a favorite color. He has never heard of people preferring a color above another.