Breakfast at Tiffany's (1961)
Based on Truman Capote's novel (also entitled Breakfast at Tiffany's), the movie follows an eccentric, Holly Golightly as she falls in love with a struggling writer, Paul Varjak, who moves into the same apartment building as her. Holly Golightly's main source of income consists of socializing with wealthy men and regular visits to Sing Sing Prison in order to provide for her brother when he gets out of the military. Her lifestyle starts to change as both she and Paul develop feelings for each other.
This movie is arguably one of Hepburn's most well-known film. Marilyn Monroe was originally offered to play the role of the Holly Golightly. She declined the role, so the role went to Hepburn. She was advised not to take the role as Golightly's party girl persona might be damaging to Hepburn's image. However, the film would only increase her popularity.
My Fair Lady (1964)
This movie follows a girl, Eliza Doolittle with a cockney accent. One day she overhears Professor Higgins brag he would be able to teach Doolittle to speak so well, that she would be able to pass as a member of high society.
My Fair Lady was originally on Broadway, starring Julie Andrews. When it was announced that the musical would be adapted into a screenplay, audiences favored and thought Andrews to play Doolittle, but much to their shock, Hepburn landed the role since the director wanted her to play Doolittle.