Ability over Appearance: Emily is an American in the book but becomes British in the film to accommodate Emily Blunt. Her performance was widely praised, and there were very few complaints about the change as a result.
Denied Parody: Miranda bears a striking similarity to Vogue editor Anna Wintour, for whom Weisberger was an assistant, but the author maintains that she is a composite of fiction and various stories of her friends' first jobs.
Dyeing for Your Art: Anne Hathaway first gained ten pounds, but was then told to lose them and she would be padded for Andy's 'fat scenes'. Emily Blunt also had to lose weight too. The two actresses claimed they were starving during production.
Enforced Method Acting: Meryl Streep went up to Anne Hathaway on the first day and said "I think you're perfect for the role and I'm so happy we're going to be working on this together" - and then warned her that would be the last nice thing she said until production finished. She also kept her distance from the other cast members. Emily Blunt joked that as soon as the film wrapped, Meryl ran across the car park to her to say "you were great!"
Throw It In!: The line from Miranda was originally going to be "everyone wants to be me". Meryl Streep disliked the line and found it too dramatic, and changed it to "everyone wants to be us" at the table reading. The change stuck.
Unintentional Period Piece: One of the "impossible" tasks that Miranda assigns to Andy is to acquire a manuscript to an unpublished Harry Potter book for her kids, which became dated in the year after the film released when the final Harry Potter book was published.note Note that while the films release year indicates they were talking about "Harry Potter and the Deathly Hallows" they never actually say that its the seventh book; just unpublished Harry Potter manuscript. Its only in a "blink-and-youll-miss" moment with the twins on the train that shows the manuscript is indeed "Harry Potter 7". Given that other Harry Potter stories in the official franchise have been published since the film was released, had that moment not happened they could have narrowly avoided it.
An extended version of the scene where Miranda opens up to Andy would have her giving her backstory - a different one from the book. She would claim to have been born in Pearl River, New York and started out as an assistant like Andy.
Stanley Tucci did several different versions of the "gird your loins!" take, throwing different lines out. One of them was "tits in!"
Graham Norton auditioned for the role of Nigel, which he humorously confronted Stanley Tucci over on his chat show.
This film is one of the most expensively costumed movies ever. The wardrobe budget was $100,000, but many top-level designers agreed to provide their latest and most stylish outfits for free. It is estimated that at least $1 million worth of clothing was used in the film.