Cult Classic: The film didn't make much money and isn't exactly a household name like other teen horror moves of its ilk, but it has a very dedicated fanbase.
Draco in Leather Pants: A lot of fans seem to ignore the fact that even before being bitten, Ginger's an unpleasant, sullen girl (albeit one with a huge soft spot for her sister), and after being bitten, she's a bloodthirsty monster. The fact that she's very charismatic and charming in a weird, offbeat kind of way, and her actress is extremely beautiful certainly helps.
Evil Is Sexy: Ginger. She may be a murderous monster, but she is played by Katharine Isabelle. (And, let's be real, the dour clothes and attitude don't detract from her beauty in the slightest.)
Fan-Preferred Couple: The most popular fan pairing is easily Brigitte and Ginger, despite the fact that they're sisters. Brigitte/Sam is also very popular, and the actors playing them have plenty of onscreen chemistry despite their characters remaining platonic.
Follow the Leader: One of the criticisms given of the later horror film Jennifer's Body was that its plot (two close female friends, one of whom turns into a monster and must be stopped by the other, less pretty one) was very similar to that of this film.
He's Just Hiding!: Some fanfiction involve Sam surviving Ginger's attack and being a werewolf himself.
Hollywood Homely: Averted; Bridgette is convincingly dowdy. They do a very good job of making Emily Perkins (Bridgette) look unattractive, when you consider just how gorgeous she is in real life.
Jerkass Woobie: Ginger. She's a Jerkass through and through for most of the film, although less so to her sister, but as the full moon approaches, Ginger seems to grasp more and more what is happening to her, culminating in the scene where she attempts to chop off her own tail and winds up crying in Brigitte's arms, consumed by fear. It's about the only point where the audience would be willing to risk giving Ginger a hug. Which makes it all the more tragic when Ginger's new murderous side overrides her personality.
Moral Event Horizon: After one Accidental Murder, and an offscreen killing with unclear circumstances, Ginger finally sheds what's left of her internal humanity when she brutally murders the janitor with no provocation apart from him stumbling upon a body, and has absolutely no remorse whatsoever. After that, the physical wolf transformation is merely a formality.