Gillian Anderson
Role: Cersei Lannister (rumored)

Casting director Nina Gold told Vanity Fair in 2017 that Anderson is one of her favorite actresses and Gold asked her to audition, or outright offered, an unspecified role on Thrones (likely Cersei, perhaps Catelyn Stark). 

However, Anderson turned the chance down. The American-British actress told The Daily Mail in 2013, "My 18-year-old cannot believe that I would turn down Game Of Thrones or Downton (Abbey) — things she loves to watch. But if I am going to be spending that amount of time working on something, I would rather be working with a director like Martin Scorsese."

Who got the role: Lena Headey