Blair kids Dan for not knowing who Givenchy is. Hubert de Givenchy founded the fashion house of Givenchy in 1952 and was famous for being the designer of choice for icons such as Audrey Hepburn and Jacqueline Bouvier Kennedy.
Whilst getting ready, Serena tells Blair that her secrecy over her new internship, that, "This is like living with Don Draper.". Don Draper is a fictional character from the TV show, Mad Men (2007), who was played by Jon Hamm. One of the recurring characters in the show was Beth Dawes, who was played by Alexis Bledel, Blake Lively's (Serena van der Woodsen) co-star and longtime friend from the movies, The Sisterhood of the Traveling Pants (2005) and The Sisterhood of the Traveling Pants 2 (2008). They played Bridget Vreeland and Lena Kaligaris respectively.
The title of this episode is a play on the title of the movie "Donnie Darko".