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." As revealed in "Graybles 1000+", Cuber is an alien living 1000 years in the future, which was first hinted at when he said the stories seen in "Five Short Graybles" are tales from "the days of old." 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, which in fact is a grayble for bravery, that floats next to the hat. 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.
- "Five Short Graybles" (debut)
- "Five More Short Graybles"
- "Another Five More Short Graybles"
- "Graybles 1000+"
- "All's Well That Rats Swell" (title card only)
- "Have You Seen the Muffin Mess" (title card only)
- "Sow, Do You like Them Apples" (title card only)
- "The Gift That Reaps Giving" (title card only)
- "Five Short Tables"
- 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. In the episode Graybles 1000+, it is proved that Cuber lives in future.
- 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.
- The cube rotating beside Cuber's antenna is the same shape as the 'Glob' universe, as revealed in the episode where the multiverse was displayed and the shape of Glob's spacetime/universe was revealed. (citation needed).
- His name, Cuber, is similar to Cubert Farnsworth's name from Futurama.