A very good read from Nathan Rabin who did indeed come up with the phrase to describe Kirsten Dunst's character in Elizabethtown. Key quotes:

It's an archetype, I realized, that taps into a particular male fantasy: of being saved from depression and ennui by a fantasy woman who sweeps in like a glittery breeze to save you from yourself, then disappears once her work is done.

The trope of the Manic Pixie Dream Girl is a fundamentally sexist one, since it makes women seem less like autonomous, independent entities than appealing props to help mopey, sad white men self-actualize. Within that context, the phrase was useful precisely because, while still fairly flexible, it also benefited from a certain specificity. Claire was an unusually pure example of a Manic Pixie Dream Girl — a fancifully if thinly conceived flibbertigibbet who has no reason to exist except to cheer up one miserable guy.

Then Zooey Deschanel strummed a ukulele and became a Hollywood It girl and suddenly the MPDG was everywhere. During one particularly strange day in 2011, I read that Cameron Crowe (the man behind “Elizabethtown,” as well as “Almost Famous” and much else) was asked about the phrase and replied, “I dig it … I keep thinking I’ll run into Nathan Rabin and we’ll have a great conversation about it.”

So I’d like to take this opportunity to apologize to pop culture: I’m sorry for creating this unstoppable monster. Seven years after I typed that fateful phrase, I’d like to join Kazan and Green in calling for the death of the “Patriarchal Lie” of the Manic Pixie Dream Girl trope.