|First appearance||6: Irony|
Cueball is a stick figure character in xkcd, distinguished from other characters by having no distinguishing features (including no hair or hat). The name is unofficial, but used here at explain xkcd or at the xkcd forum.
Like other xkcd characters, Cueball doesn't necessarily represent the same character from comic to comic, and is not necessarily a unique character in any given strip. Instead, he represents a generic everyman. In several comics, there are multiple such stick figures, any of whom could be called Cueball.
One version of Cueball, though, has had lots of computer problems...
There was at one point a community portal discussion of what to call Cueball and what to do in the case of a comic with more than one Cueball. Nothing much came of it - the standard practice is to name the main protagonist (the one with the funniest/defining part) as Cueball and then name the other(s) friend etc. If it is impossible or unnecessary to discern any of them from the other then none should be called Cueball. Clarity of the explanation and ease of understanding should be carefully considered when making this judgement.
Several of the comics about cancer have Cueball representing Randall himself.
The character is never actually referred to as Cueball in xkcd; the name was developed by early contributions to explain xkcd. It refers to the visual similarity of Cueball's head to a billiard ball. Randall's transcripts usually refer to the character as "Man 1", and so on, although he has at one time referred to him as not terry in his official transcript for 989: Cryogenics. A few comics give a Cueball character a name, but only one name, Rob, appears several times (12 in total) for a Cueball. The debate mentioned above was mainly about whether all other Cueballs should be retroactively renamed "Rob". Following the same logic that resulted in the "Cutie" character (the female version of Cueball) being renamed Megan, an argument can be advanced for renaming Cueball as Rob, but that suggestion was not accepted.