Andrea is Daria's goth classmate at Lawndale High. She was first seen in the very first episode of Daria, Esteemsters, as a member of Mr. DeMartino's history class. The mystery goth was an unnamed background character until the fourth Daria episode, Cafe Disaffecto.
Young Woman of Mystery
Unlike many other characters in Daria, virtually nothing is revealed about Andrea during the five years that Daria ran on MTV. The tone is set in "Cafe Disaffecto with the end of Andrea's coffeehouse poem, which concludes "I'm here. But where are you? Sure, I see your body. Anybody home in that rotting bag of flesh?"
The few hints throughout the series regarding Andrea confirm her cynical outlook on life. Her locker is adorned with a skull and crossbones poster and a biohazard poster (Arts 'N Crass). She is happy to make a bet on Mr. DeMartino getting injured in the DJ/Faculty roller hockey game (and it is implied that she wins the betting pool). When Quinn foolishly tries to raise money from Lawndale High Students so she can get plastic surgery (Too Cute), Andrea asks Quinn if she's worried there might be a hell.
Andrea's parents make her work at Payday (Mart of Darkness), and she's not happy about it. In (Daria's Inferno), Daria gives Andrea a cowbell to put in her nose to annoy her parents, and Andrea says: "That is irritating! Perfect." Daria's Inferno is Daria's dream, but if this is an indication of how seriously Daria takes Andrea and her goth sub-culture, it could be a reason why the two aren't friends or even acquaintances, even though they seem to have a lot in common.
The only other hint of Andrea's inner life comes from cartoon strips in The Daria Database drawn by "Andrea 666" called Gothic Nights: The Adventures of Queen Hecuba. The three cartoon strips deal with Queen Hecuba (a thinner, more regal version of Andrea) vanquishing enemies consisting of Upchuck, Kevin, the Lawndale High School faculty (except Janet Barch) and Mack Mackenzie.
While the reasons for her antipathy toward the others is understandable, her beef with Mack is puzzling—the other enemies are all tricked into defeat and humiliations, while "Sir Mack the Fearless" is Hecuba's "archenemy" and requires fighting. That strip ends with a spectral version of Barch arriving, which terrifies Mack into retreat and causes Hecuba to give Barch a job; this makes Barch the only teacher given a positive role in the strip. Does Andrea like Barch?
In one strip, Queen Hecuba seeks to rescue her "beloved brother Damien" from an evil king. It is unclear if the unseen Damien is based on a real-life brother of Andrea's.
Daria dreams of Andrea working for Upchuck and massaging his feet in "Murder, She Snored." Why? We don't know.
Andrea in Mart of Darkness
At the end of Mart of Darkness, Daria and Jane locate a clerk at Payday that seems to be avoiding them. The clerk is revealed to be Andrea, who states that she was trying to avoid Daria and Jane because she didn't want to hear them mock and "cut her up" verbally for working at Payday, a hated job imposed by her parents. However, Daria and Jane state that, as far as they are concerned, they never saw her at all. Andrea's secret is (theoretically) safe.
Andrea in Is It College Yet?
In Is It College Yet?, Upchuck hits on Andrea and offers to remove her from Jodie's graduation party. Andrea is surprised that Upchuck is trying to hit on her ... and then accepts Upchuck's offer, much to Upchuck's surprise. There is no reason for Andrea to accept the offer, and nothing is known about what happened next.
Andrea in Fanfiction
In some early Daria fanfiction, Andrea was seen as a natural ally of Daria and Jane. In some stories, Andrea has the sort of "omnicapability" that was granted to Daria, making her a master of martial arts, firearms, and other really cool things. The fact that virtually nothing was known about Andrea facilitated such stories, as Andrea was simply a blank slate upon which any sort of characterization could be projected. (Tiffany is another such blank slate, although less appealing.)
Sometimes Andrea is given the fanon last name "Hecuba," from the Gothic Nights strip. Another popular fandom name is 'Thorne' (which may be connected to her having a brother named Damien, "Damien Thorn" is the evil child in The Omen). Some fanfic writers use both, for "Hecuba-Thorne."