Catelyn Stark was a critical part of Game of Thrones' first three seasons, and she was originally supposed to be played by a different actor — but I just can't imagine it in hindsight. In fact, it's hard to envision any version of Game of Thrones other than the one we got. However, HBO's fantasy series initially looked quite different. The show's original, unaired pilot episode saw a different star playing Daenerys Targaryen before Emilia Clarke. It also contained a number of details that were later changed, like the costumes and hair, as well as the White Walkers talking (via SlashFilm).