Story structure
Manic Pixie Dream Girl
Nathan Rabin's 2007 label for a stock character: a young woman with eccentric quirks serving as an everyman protagonist's romantic interest.
A Manic Pixie Dream Girl (MPDG) is "a stock character in fiction: a young woman with eccentric personality quirks who serves as the romantic interest for an everyman protagonist." The American film critic Nathan Rabin coined the term in 2007 after observing Kirsten Dunst's character in Elizabethtown (2005), and his charge is the useful one: the type is one-dimensional, "existing only to provide emotional support to the protagonist, or to teach him important life lessons, while receiving nothing in return." Natalie Portman's character in Garden State is his other case, and Audrey Hepburn's Holly Golightly in Breakfast at Tiffany's is filed as a vintage instance.
The term is a diagnosis of a character who has no life apart from her function, the same structural flaw the Mary Sue flags from the opposite direction: one is flawlessly adored, the other adorably flawless, and neither has wants of her own. The cure is interiority, a want, a cost and an inner life the reader can enter, which is the work of how to create characters. Handle the label with care: Rabin apologized for coining it in 2014, and critics have called its use misogynistic, so aim it at the draft, not the person.