Doctor Who (series 4) Astrid Peth, who died during the events of the episode. The companions in the regular series had all been in the lead companion role previously: the primary role of Donna Noble, who was introduced in "The Runaway Bride", was played by Catherine Tate for all thirteen episodes. Her return was announced by the BBC on 3 July 2007. Freema Agyeman, who portrayed the Doctor's companion Martha Jones in series three, returned for "The Sontaran Stratagem", "The Poison Sky", "The Doctor's Daughter", "The Stolen Earth" and "Journey's End". Billie Piper, who played Rose Tyler from the first episode of the new
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