Marker is a green-colored marker pen with a big green cap covering her felt-tip. The container is white, and she has green colored areas on the side of her body. She has black-dotted eyes, as well as a black mouth and limbs.
In Time Wasters, Eraser Wash panics about the disappearance of Cap, she asks Marker and her friend Glue Bottle for help, also explaining the story of her loss. Marker responds to her call for help, telling her about sighting Cap at the teacher's desk. She then jumps away from a building block, landing in Glue Bottle's arms as he yells at Pin, demanding him to stop causing trouble. Pin ignores Glue Bottle's request and proceeds to continue pushing off blocks. After telling him to get down from where he is pushing the blocks off of, Marker asks Mini Eraser to stop Pin's mischief, but Mini Eraser is too lazy to do so and tries to convince Marker he'll do it later. Marker becomes angered and tells him to do it immediately before falling due to one of Pin's blocks. Eraser Wash then leaves, telling her to have good luck with her skirmish.
Marker can be quite demanding and bossy, as shown to her reaction to Pin throwing off building blocks.
- Ink: TBA
- Glue Bottle: She and Glue Bottle seem to be friends.
- Mini Eraser: Marker once demanded Mini Eraser to do something about Pin's antics.
- Eraser Wash: Marker once helped Eraser Wash find Cap, but only gives a mere hint.
- Pin: Marker got pissed at Pin's misbehavior.
- Marker and Glue Bottle seem to be best friends.