Furrball is a young, blue male cat with a hole on his right ear and a bandage on his tail. He attends Acme Looniversity and lives in ACME Acres. Furrball's mentor and favorite teacher at school is Sylvester, although the two's similarities only seemed to include their appetites.
Furrball usually lives in a cardboard box in a back alley or as an unwilling pet of Elmyra Duff (in spite of the latter, he was absent from the spin-off Pinky, Elmyra, & The Brain). Unlike most of the other characters, he does not speak and is a typical pet character. Furrball spends much of his time futilely trying to eat Sweetie Bird, a pink canary; and Li'l Sneezer, a baby mouse with many allergies and hurricane-force sneezes. However, there has been one occasion where Furrball gets the last laugh on Sweetie when he had Arnold the Pit Bull to be hypnotized to chase her after recovering from the hypnosis she put him under. As the beginning indicates, Furrball is unlucky, emphasized with him being unexpectedly squished into the dirt by a falling piano. Furrball has also proven to be one of the most versatile characters on the entire show. Some of his many misadventures include getting a pair of enhanced 3-D glasses glued to his head, being hypnotized into trying to eat Arnold the Pit Bull for supper, becoming the host of a family of singing Italian fleas, being amorously pursued by Fifi La Fume after involuntarily winding up with a white stripe down his back, and being chased by the temporarily transformed Sweetie, a large, carnivorous, evil-eyed, feathered Mr. Hyde/Dr. Frankenstein monster who wants to eat Furrball. Furrball also has a bad encounter with Byron Basset, who tries to prevent Furrball from trying to eat some baby birds whom he's protecting. Usually, though, the two of them are seen as living peacefully together, not paying much attention to each other and minding their own business. Although several appearances compare him to Sylvester, there were a few cartoons that cast him in a more sympathetic light. In these appearances, Furball is an abandoned alley cat, constantly looking for a home. The shorts would depict his misadventures in this goal, such as being mistaken for a dog by a blind couple; situations that were humorous, but also gathered sympathy for the character. He was a lonely cat against the world, but never gave up hope, much like legendary actor Charlie Chaplin. As Furrball hardly ever spoke throughout the show, his typical cat sounds are provided by Frank Welker. However, it is revealed that he speaks in three episodes. In the episode Duck Trek (in which Furrball played a spoof of Star Trek's Leonard McCoy), he was voiced by Rob Paulsen (actually, he was lip-syncing). In the episode Buster and the Wolverine (a spoof of the classic musical children's story Peter and the Wolf), it is revealed that Furrball is voiced by his regular voice actor, Frank Welker. In the episode Hare Today, Gone Tomorrow, he speaks precisely one word ("years," referencing how long he has been held captive by Elmyra; of course, he'a exaggerating), with his voice again being provided by Welker. At the end of one episode after he and Dizzy Devil expose the Perfecto Prep students' cheating at a baseball game, they both said the following sentence at a victory celebration: "We love baseball." Through the majority of the show, Furrball is mute. Furrball's end tag credit is him roaring at the screen like a lion, before covering his mouth and letting out an apologetic meow. Furrball made a cameo appearance in the Animaniacs short "Home on De-Nile", where Cleopatra called him the worst cat of all.