3. Jennifer Ehle
Another actor who was, in fact, Jennifer Ehle appeared as Catelyn Stark in the Game of Thrones pilot, but when the time came round to shoot the full episode order she was nowhere to be seen. Michelle Fairley took over and Ehle - who still claims to be a fan of the show - went onto appear in Steven Soderbergh's Contagion and co-star in CBS' A Gifted Man (cancelled after its first season). On a peculiar side note, Ehle has also appeared in a notable production of Pride and Prejudice - not the Joe Wright one, but the 1995 BBC version alongside Colin Firth - for which she won a BAFTA. Though having a young kid may have prevented Ehle from committing to a 13 episode shoot in the likes of Iceland and Ireland, she did get to act alongside Firth again in The King's Speech as the wife of his character's speech therapist. Ehle doesn't seem to have borne any bitterness: as she says in the interview linked above, "clearly the show is what it was meant to be". It's nice to see someone respond to losing a major role with such class.