|Introduced in||"Five Short Graybles"|
|Latest appearance||"Another Five More Short Graybles"|
|Voiced by||Emo Philips|
Cuber is a character who speaks in the beginning and end of the episodes "Five Short Graybles," "Five More Short Graybles," and "Another Five More Short Graybles." He seems to know Finn, Jake, BMO, Tree Trunks, Marceline, Gunter, and Princess Bubblegum but calls Ice King "the blue guy" and Lumpy Space Princess "the other thing." He may be from the future, considering that he says the stories seen in "Five Short Graybles" are tales from "the days of old." This can be supported by the fact that his clothes and room look advanced, though similar technology can sometimes be found in Ooo. He speaks a variety of non-English terms (see quotes) but mostly speaks English.
Cuber's skin is light pink, and his head is significantly larger than the rest of his body. His facial features are similar in appearance to most characters', albeit spread apart across his large face, leaving him with a comically small mouth in proportion to his other body parts. He wears a little hat with a small, spinning purple cube that floats next to it. The hat itself is a hemisphere with a small, bent rod coming from the top. The hat is the same color as his robe, which is light salmon colored. His robe has small green, mauve and light blue squares on its front top half. Its chest also has a line with many 90 degree angles that dividing it approximately down the middle. The line ends abruptly at the beginning of the bottom half of his robe, suggesting that the top and bottom halves of his robe could be separate.
- The title card of "Five Short Graybles" features a giant crystalline structure in the Galaxy of Flavors with Cuber's silhouette appearing in its window. The title card also features Finn and Jake, however, which contradicts his suggested place in Ooo's timeline. Title cards often depict scenarios that do not actually happen in the episode, so it is unknown whether any part of this image can be taken as fact.
- The hologram of the Earth in Cuber's room on the right side shows its crater.
- He is one of the three characters to break the fourth wall (the first being Ice King in "Beyond this Earthly Realm" and the second being Finn in "A Glitch is a Glitch"), as he addresses the audience and is the only character in the series to constantly break the fourth wall in every episode he appears in.
- The Holo-Pyramid Viewer shown is a tetrahedron with only four sides, but there are five Graybles. Rotating the Viewer seems to change the photo on one of the sides to fit all the Graybles.