Warning: MASSIVE Spoilers ahead for Doctor Who season 15, episode 6, "The Interstellar Song Contest."Carole Ann Ford's return as Susan in Doctor Who season 15, episode 6, "The Interstellar Song Contest," is exciting for many reasons, but factoring into Ford's comeback is the fact that it pays off a moment from very deep into the show's multi-decade history. As a pivotal figure in Doctor Who's classic era, Ford's character was the first companion to the story's primary protagonist, and remains the only known biological relation of the Doctor. Susan's cameo in "The Interstellar Song Contest" is her first Doctor Who episode not to also include the First Doctor, who left her behind in 1964.