Byron "Buster" Bluth is the youngest son of George Sr. and Lucille, and as a result was always babied by his mother.  Throughout the series it is implied that George Sr.'s twin brother, Oscar, is actually Buster's father.  But really, who knows with Arrested Developement?

Unable to actually be productive, Buster spends his life as a perpetual professional student studying such important topics as cartograph and Native American tribal ceremonies.

Despite being extremely socially inept and falling victim to frequent panic attacks, Buster is actually quite intelligent.  Buster also managed to date Lucille 2 (Lucille Austero), a woman much older than him for a brief period.

During season two, Buster loses his hand to a seal and is normally seen with either a hook or a prostethic hand.

Buster Bluth Quotes

(holding stuffed animals) These are my awards, Mother. From Army. The seal is for marksmanship, and the gorilla is for sand racing. Now if you'll excuse me, they're putting me in something called Hero Squad.

Buster

Narrator: The family continued to chant "speech, speech, speech" for no one in particular.
(clapping ceases)
Michael: Gee, after all that, I was kinda hoping somebody would make a speech.
Buster: Speech! Speech! Speech! Speech!
Michael: I'll say something.
Gob: Typical.

Arrested Development Quotes

(holding stuffed animals) These are my awards, Mother. From Army. The seal is for marksmanship, and the gorilla is for sand racing. Now if you'll excuse me, they're putting me in something called Hero Squad.

Buster

Lucille: I'll be in the hospital bar.
Michael: Uh, you know there isn't a hospital bar, Mother.
Lucille: Well, this is why people hate hospitals.