"The Manic Pixie Dream Girl is a trope we are quick to criticize because of its reductive placement of the role of women and interpretation of their actions and identities. It's a categorization not fondly regarded by the actresses playing these characters for similar reasons, though it is a trope that is continuously defaulted to when we have a lonely, loathsome male protagonist, in the midst of his male rite of passage: the existential crisis. It is also a trope that racially limits our interpretations of what constitutes a woman and who qualifies to play major female characters. Annie Hall is no such character."
Amen to that. Read it and even if you haven't seen this incredible film, you'll want to.