The Devil Wears Prada is a simple little comedy that appears to have almost nothing going for it. The hero doesn't go through much character development. She gets caught up in trying to be successful, forgets her friends and her boyfriend, and ends up opting for integrity and a substantial career instead of climbing the executive rungs of the fashion business. It's all very predictable and trite. But this obvious character change is there to give the writer a clean line on which to hang a sequence of funny bits. The secret to the success of this comedy is found in three structural elements: a horrible but believable opponent, a unique and authentic story world, and a psychology the audience is all too familiar with.
A great opponent is just as important in a comedy as it is in an action story. Since comedy structure is based on snowballing nightmares (see the Comedy Class for how to set this up), you always have to start with a powerful opponent who can generate the nightmares. A great comic opponent is not literally deadly like an opponent in an action story. But she must be socially deadly, able to inflict severe humiliation or loss. Here, the hero's boss, Amanda (played perfectly by Meryl Streep), is a monster with no end of ways to torture her assistant and make her feel small.
The comic scenes and lines come out of a unique story world - the fashion industry - that is both foreign, and thus surprising to the audience, but is also part of our everyday lives. A sense of authenticity is very valuable in storytelling because it gives the audience the exciting sense that they are peering into a hidden world. When that world is fashion - the clothes we wear to look good - that excitement is magnified.
The comedy also relies heavily on a deep psychological scar, especially for women, that is embedded in American culture. This is the pressure to be thin and beautiful. A lot of the fun in this movie comes from the fortunate casting of Anne Hathaway in the lead, an actress more beautiful than most supermodels. But I'm sure the script was written from the beginning based on the assumption that a beautiful actress would play the part. So when the fashionistas remark with disgust that the Anne Hathaway character is a size 6!!, the joke is funny because it is both absurd but also, within this world, totally real. With each joke the audience senses that if it can happen to a "normal" woman who is this beautiful, what chance do I have. A joke or gag is always meant to create laughs by diminishing the character. If you can also give the audience some recognition or revelation about their own life at the same time, the joke is ten times more effective.
