On the first day of filming, Meryl Streep told Anne Hathaway, "I think you're perfect for the role. I'm so happy we're going to be working together." Then she paused and followed it up with, "That's the last nice thing I'll say to you." And it was.
Despite multiple fashion designer loans, Patricia Field spent more than $1 million on costuming, making it the most expensively-costumed film in history. Field received her sole Oscar nomination for her work on this film.
The only contact production had with Vogue was Jess Gonchor, the production designer, who snuck into their offices to get a look at Anna Wintour's office. He was able to re-create it so authentically that it is said that Anna redecorated hers immediately after the movie came out.
Anna Wintour, the editor of Vogue (and the inspiration for Miranda Priestly), was not invited to the premiere. She did, however, attend an advance screening for the press along with her daughter, dressed head-to-toe in Prada. Wintour's daughter could be heard nudging her through the screening: "They got that right!" Although never commenting on it publicly, she reportedly really liked the film despite initial skepticism.
All costumes were sold off at an auction for research of breast cancer. Anne Hathaway bought the green dress her character gets to wear. The one item Meryl Streep kept was her sunglasses, which she used again as Donna during the famous "Money Money Money" scene in 2008's Mamma Mia!.
Lauren Weisberger: (at around 54 mins) The author of the book on which the film is based has an uncredited cameo role as the twins' nanny.