Doctor Who (2013 specials) Doctor", saw the departure of Smith from the series and the introduction of Peter Capaldi as the Twelfth Doctor. "The Day of the Doctor" features the return of the Zygons for the first time since "Terror of the Zygons" in 1975. "The Time of the Doctor" draws together a number of plot threads that have run through the series since the Eleventh Doctor's first episode in 2010. <onlyinclude></onlyinclude> In "The Day of the Doctor", Smith and Coleman star alongside David Tennant and Billie Piper; Tennant reprised his role as the Tenth Doctor, while Piper, although credited as playing Rose Tyler,
Doctor Who spin-offs was produced by animation company Nelvana in the 1980s, but the series was not produced. CBBC originally expressed an interest in a "Young Doctor Who" series, chronicling the childhood of the Doctor. Russell T Davies vetoed this concept, saying "somehow, the idea of a fourteen-year-old Doctor, on Gallifrey inventing sonic screwdrivers, takes away from the mystery and intrigue of who he is and where he came from,". He instead suggested "The Sarah Jane Adventures" (see above). A further spin-off of "Doctor Who"—"Rose Tyler: Earth Defence", a 90-minute special that could possibly become an annual event—was cancelled by Davies at a