By Charlotte Tutton Doctor Who viewers think a number of clues have given away the return of an original character on the BBC series. From a telling comment made by the Doctor to Ruby Sunday to the mystery surrounding her identity, there’s also the fact an actress named Susan Twist has been credited for more than one episode, all in different roles. Why is this significant? Susan has appeared in a few scenes in different episodes since Ruby debuted as the new companion, the latest being an episode where Ruby and the Doctor sang about “a twist”. Also in this episode the Doctor talked of his los…