Bob
Bob is the name of a recurring background character (or "backgrounder"), given a name in Cafe Disaffecto by happy accident after fans found a seating chart was legible. He's in a number of Daria's classes.
Bob is a standard punk and in "Jane's Addition", you can see him at the Zon smoking and drinking despite being too young. The obnoxious DJ's of Mental in the Morning met with his visible approval in "Jake of Hearts". So far so normal, except he repeatedly shows up at school behaving: he's even on the yearbook in "The New Kid" and helps Mr. DeMartino pack up the classroom in "Is It Fall Yet?" Most at odds with his image and bad habits, he's one of the guys who buy the Fashion Club's newsletter in "The Story of D" (but don't read it).
Bob's arm tattoos change from episode to episode, even appearing and disappearing, as a result of animation errors.
Fandom
Bob was mostly absent in fanfiction until "God Save The Esteem", picked up by the author while browsing (now lost) The Angst Guy site Backgrounders; he played a rival punk, who studied at school so he could raise hell elsewhere. Bob appeared in a number of other fanfics after that, first in "Lawndale Fighting Championship" as a hardcore wrestler (a face, no less). What helps him above all other backgrounders, apart from his distinctive look, is we actually have a name for him.