There are a few articles (from The Onion AV Club, Jezebel and Broadsheet out there on the "Manic Pixie Dream Girl" - the sort of character from Garden State, Almost Famous or Sweet November that's just a quirky cipher for the male protagonist to get infatuated with.
To me, the MPDG is just an especially egregious example of what I've taken to calling the "Designated Hot Girl" - a female character who is the primary focus of the male gaze, both diegetic and non-diegetic. In other words, all the straight guys in the show are attracted to her, and her attractiveness is played up for the presumed-to-be-male audience. (Star Trek, the original series notwithstanding, is a notable offender in this regard - Deanna Troi, Seven of Nine, and T'Pol are all Designated Hot Girls.) Often, it's rather inexplicable why one character gets the treatment and another doesn't, since every female character between 15 and 50 is going to be some form of "Hollywood pretty."
(It occurs to me there's a slight difference - the MPDG attracts the attention of the hero, because he's a sensitive soul uniquely positioned to understand how amazing she is; the DHG attracts the attention of *everyone* to a degree unwarranted by her actual appearance, actions or traits.)
The MPDG is especially bad because her sole raison d'etre is to be "to teach broodingly soulful young men to embrace life and its infinite mysteries and adventures." She's all object and no subject, because as a protagonist she doesn't work. Though one common trope is to point out how the male lead - and, by extension, the audience (though not the *writer*) - has denied her agency.
Compare the MPDG with, say, the Tenth Doctor from Doctor Who. There have been several women characters on the show (Rose, Martha, Sarah Jane) who talk about how the Doctor flits in, changes their lives, and then leaves again, and indeed it's not too hard to conceive of a retelling that casts him as a Manic Pixie Dream Boy. But that's *not* the story that's told, and in fact by the end of series 2 *Rose* is retconned into a form of Manic Pixie Dream Girl, that shows a universe-weary Time Lord how to love.
1 year ago