TRISTAN: You don’t want me to tell Dean that we kissed.
RORY: By George, I think he’s got it.
Rory is referencing the 1964 musical comedy-drama film My Fair Lady, adapted from the 1956 Lerner and Loewe stage musical of the same name, which was based on George Bernard Shaw’s 1913 play, Pygmalion.
In the film, phonetics professor Henry Higgins (Rex Harrison), has a bet that he can teach a Cockney flower girl named Eliza Doolittle (Audrey Hepburn) to speak with an upper-class accent. At first she makes no progress, but one day has a sudden breakthrough, leading Higgins to exclaim delightedly, “By George, I think she’s got it”.
My Fair Lady was a critical and commercial success, becoming the #1 film of 1964, and won eight Academy Awards, including Best Picture, Best Actor, and Best Director (for George Cukor). It is considered one of the greatest musicals, and one of the great films of all time.