Temporary note: I knew I should've posted this yesterday.
She's quirky, bubbly, often childlike, and lives a seemingly carefree existence. Of course, she often has underlying psychological issues, but these do not concern us much. No, this collection of quirks in bohemian clothing exists solely for the male protagonist. He's living a dour or uninteresting life, and she enters it to inspire him and show him what he can become.
Having helped him find himself, she generally disappears.
Film critic Nathan Rabin first used the term in 2007 when reviewing Elizabethtown, as a descriptor for Kirsten Dunst's character Claire Colburn. Rabin noted she was part of a larger trope, the quirky girl who "exists solely in the fevered imaginations of sensitive writer-directors to teach broodingly soulful young men to embrace life and its infinite mysteries and adventures." He now regrets it. The term took on a life of its own, and got used in ways he now finds discomforting. Principally, however, it gets applied to quirky female characters from quirky or indie films, especially those from from around the turn of the millennium. Layla (Christina Ricci) from Buffalo '66 (1998), Penny Lane (Kate Hudson) from Almost Famous (2000), Sam (Natalie Portman) from Garden State (2004), and Anna Barnes-Leatherwood (Charlize Theron) A Million Ways to Die in the West (2014) would all qualify as Manic Pixie Dream Girls.
Other oft-cited examples prove more problematic. Summer Finn (Zooey Deschanel) from 500 Days of Summer, Clementine Kruczynski (Kate Winslet) from Eternal Sunshine of the Spotless Mind, Ruby Sparks from Ruby Sparks, and Margo Roth Spiegelman (Cara Delevingne) from Paper Towns (2015) often make the list, but those films, with varying degrees of success, examine the trope and find it wanting. Ramona Flowers from Scott Pilgrim vs. the World has more than a little of the MPDG about her. She's far more developed in the original graphic novels, and the movie's ending, arguably, undercuts the trope. The movie's alternate ending, alternatively, reinforces it.1 The title character of the novel (and forthcoming film) Looking for Alaska might qualify. Audrey/Lulu (Melanie Griffith) from Something Wild (1986)? Possibly. Holly Golightly in Breakfast at Tiffany's? The Muses? The term now gets thrown around so liberally that any quirky female character who assists a male character or (more damaging) quirky female who draws breath now risks getting identified as a MPDG.
The character presents a number of problems, already highlighted by previous write-ups. Rabin himself notes the use of the term may even reinforce the kind of sexism his identification of the trope decried. By applying it broadly, critics may point out when a character is merely a male fantasy, but it may also lead viewers and readers to reduce more complex characters-- or, you know, actual human beings-- to male fantasies.
As with all character-related tropes, it presents the most trouble when it gets applied to actual human beings, who may aspire to be more than adjuncts to someone's personal development.
Men, of course, can also be presented as adjuncts to a lover's character development, and lists of Manic Pixie Dream Boys can now be found. The MPDB (or G) relates to the trope of the White Knight-- in its earlier, pre-internet meaning--: the perfect man who rides into some women's life to carry her off and set everything right.2
The Manic Pixie Dream Girl has inspired other people, including a handful of indie bands who have recorded songs by that name. A writer named Tom Leveen published a YA novel entitled manicpixiedreamgirl in 2014. Poet Olivia Gatwood created an excellent performance piece decrying the character. It seems the Manic Pixie Dream Girl will not disappear any time soon, either as character or term of discourse.
1. SPOILERS! Bryan Lee O'Malley had not yet finished the series when the movie went into production, so the filmmakers shot two endings. In the other one, He ends up with Knives Chau, and Ramona dutifully disappears.
2. "White Knight" took on a second meaning, the male who supports feminist and female-oriented causes only because he's trying to look caring and sensitive so he can get laid. Of course, since that usage gets most of its play online, where there is no chance of the male making the comment ever meeting the female he's supporting, it arguably now has the third meaning of convenient term of abuse to silence men who might actually support a feminist or female-oriented cause.