Quinn is the younger sister of Daria and a freshman (later sophomore and junior) at Lawndale High School. At the age of 14½ years, Quinn was the chief nemesis for Daria for the bulk the series. The polar opposite of Daria, Quinn was perky, popular, and attractive in the eyes of her fellow classmates, much to Daria's horror and disgust.
Quinn Morgendorffer is a stereotypical self-absorbed teenage girl who is concerned mainly by clothing, shopping, and being popular. Her interest beyond such trivial things are minimum save for getting into a "Party College" with her friends. However, in spite of this Quinn does have some depth, though it's hidden by a great deal of low self-esteem in terms of her value. As she confesses to Daria in the season two episode "Monster", Quinn feels that looking pretty and being popular are the only things she is good at, hence why she focuses on them exclusively. Also she does feel some ambition towards doing better, though her efforts almost always end up getting her in trouble with her friends, who all deride the notion of intellectually bettering oneself. Still, despite Quinn's refusal to show her intelligence, she is shown to be as crafty and manipulative as her sister on rare occasions, particularly when she can get something out it.
The later seasons of the series have Quinn reconsidering her priorities and coming to value her intelligence and her family in her own way.
Relationship with Daria
Quinn has a rather adversarial relationship with Daria; the two are very resentful of the other and that their differences regarding social standing and personalities drive a large amount of the conflict in the series. Both sides love to antagonize the other (though Quinn is less open about admitting to do so) though in spite of these differences, there does exist a level of sibling love between the two, even if they refuse to openly admit it. When not openly annoying or insulting Daria, Quinn's dealings with her often resemble a business transaction such as laying out terms of requirements, expenses, exceptions, and final payment. A recurring joke involved Quinn refusing to even admit to being Daria's sister, and her friends thinking Daria was her cousin or some other vague relation, often referring to her as "that girl who lives with you." However, by the final episodes, their relationship warms considerably.
On some rare occasions the two sisters have worked together to achieve some goal, usually to get out of trouble or to avoid it. Most often these instances are delt with in a rather business like fashion, such as when Daria incites Quinn (in episode 205: That was Then, This is Dumb), with an offer of some form of payment or benefit, to gather scandalous blackmail information about their parents from the son of visiting family friends. Later when Quinn begins to uncover some such stories her response is "These have got to be worth at least 20 bucks (to Daria)."
Socially active, Quinn quickly became one of the most popular girls in Lawndale, much to the horror of her fellow members of the Lawndale Fashion Club, a clique of teenage girls who Quinn was friends with. While she had many boyfriends (even going as far as to come up with a ranking system for the men she dated), her only consistent interest lay with three teenage "jocks" from her grade level: Joey, Jeffy, and Jamie, three of her classmates who constantly followed her around and who were constantly being manipulated by Quinn for her own selfish purposes.
Sexuality and Conservatism
Even though Quinn refuses to be tied down to one guy (for reasons of wanting multiple men to serve as proverbial slaves to her every whim) as well as shown to be perfectly comfortable flirting with other guys while on dates and stealing other girls' boyfriends, Quinn is rather conservative in terms of sex itself. She has on multiple occasions rejected the sexual advances of older men and was quite shocked when she believed that Daria had lost her virginity to her boyfriend Tom Sloane. Indeed, Quinn is extremely squeamish regarding anything overtly sexual, to the extent of refusing to participate in a lesson in sexually explicit posing with men during a modeling workshop class she was involved in.
Quinn has also shown conservatism in other social activities of her peers. She does not drink, which put her at odds with a co-worker and friend Lindy in the series finale movie "Is It College Yet?".