Billy bumblers are a species of animal found in the Dark Tower universe. Since the world moved on, most billy bumblers have become feral, but intelligent examples do still exist. While some mistake the speech of the bumbler for mimicry, the creatures have an almost human capacity to feel emotion, and are very clever. Billy is a prime example of an intelligent bumbler. He is also a "twinner" or alternate version of Oy of Mid-World, the bumbler best friend of Jake Chambers.
Billy was created specifically for comic books by Robin Furth, with special permission from Stephen King. When asked if it would be possible to include a bumbler in the comic book version of the Dark Tower, King's only prerequisite was that said bumbler be related to Oy in some way.
When Roland Deschain first meets Billy, he is curled up next to the dead body of his friend, a young boy with blonde hair who bears a striking resemblance to Jake Chambers. The bumbler tells Roland that the boy's name is John, which is Jake's real name, strengthening the idea that John, too, is a twinner.
Billy becomes a travelling companion for Roland, keeping him company and also joining him in battle as the situation requires. It quickly becomes apparent to the gunslinger that the creature can understand what is being said to him, and reply intelligently to questions.
Major Story Arcs
The Journey Begins
After losing his original master, Billy decides to follow Roland, who warns the bumbler that all who have gotten close to him have died. Undeterred, Billy goes with him anyway, soon proving to be a useful companion.
The two travel to Gilead, which now lies in ruins. While there putting Aileen Ritter's body to rest, they happen upon a group of slow mutants attacking a family of bumblers. Roland and Billy jump into the fight, but while all the slow mutants are soon dead, not a single bumbler survives. Grieving for the loss of his own kind, Billy howls mournfully. It is in this moment, in which Roland realises he can relate to Billy having lost so many of his own friends and family, that the two begin to bond.
Billy ultimately gives his life defending Roland, just as the gunslinger foretold, killed by a No-Man who impales the animal in a blind rage after being bitten. In the animal's dying moments, Roland promises that there will be friends waiting to take care of him. He describes Billy as a brave warrior, deserving of more, and apologises for allowing him to meet such a violent end.