Who played Arya Stark in 'Game of Thrones'?

In which TV series is Dr. John Watson a main character? In which TV series is Tyrion Lannister a main character? Who played Cersei Lannister in 'Game of Thrones'? In which TV series is Cersei Lannister a main character? In which TV series is Arya Stark a main character? Who played Sansa Stark in 'Game of Thrones'? In which TV series is Sansa Stark a main character? Who played Ned Stark in 'Game of Thrones'?