Why? Everyone forgot once Donna turned out brilliant that she was their favourite choice for Series 4.Why Not? Is she truly a loose end? Also, is she in the show's budget? Sally Sparrow is a 100% Moffat creation, and it seems those are most likely to get a return visit from the Doctor anyway. And in all honesty, she seems just as loved by fandom (and the casual viewer, given her sole appearance's celebrated status!) as any Silurian, Archaeologist, or fat blue fellow. To the three or four people who don't know, Sparrow helped the Doctor in his first (televised) encounter with the Weeping Angels. She followed clues and actually, eventually met him before HIS first encounter with her to close up a predestination paradox and allow him to inform her previously how to help him eventually. Got that? (I love writing about this show....) Sally Sparrow is possibly the most obvious companion who never was, but also clearly has a knowledge and understanding of the Doctor that even some of his seasoned travellers can't grasp - His existence and meetings with him can be completely non-linear, and due to this she's an easy candidate to drop into a story and start asking pertinent questions, rather than working through all the usuals ("You travel through time!?!" "It's bigger on the inside!""ANYWHERE? We can go ANY WHERE? ANYTIME?"). Her story is a bit open and shut if you take the events of "Blink" by themselves. But it's hard to imagine that Sally Sparrow, a young girl eager to adventure and discovery, would just STOP after meeting a Time Lord who begs more questions than he ever answers. ("I'll explain later" most CERTAINLY doesn't count.) The problem here certainly isn't the show as it exists now - Moffat seems more likely to drop in on his own creations that he is to pay a call to Mickey Smith, Sergeant Benton, or Wilfred Mott. It's really that Carey Mulligan, Sally Sparrow herself, is a bit of a big deal now. A bigger deal than Doctor Who usually manages beyond voice acting (Michael Sheen and Sir Ian McKellen were wonderful to, er, hear, weren't they?) One Academy award nomination and several films such as "Drive" and "The Great Gatsby" on, she's the kind of name that people speculate would be in a Doctor Who MOVIE. Not the show itself. Did I bend the rules to include her? Perhaps. But think on this: a newcomer to the show is VERY likely to see or even be introduced to "Doctor Who" via "Blink". And as they consume and digest more and more episodes, they'll get more and more confused that the Chav who's gone forever keeps coming back, the lady from ER simply won't leave, and the rather camp fellow keeps popping in too (No, not the Master, I mean Captain Jack). Dorium Maldovar, Mickey Smith, Sarah Jane, Vastra and her groan-worthy Sontaran, and even this Kate Stewart person (who REALLY must confuse anyone who's never looked beyond 2005) - They all get to pop in again. Why not this wonderful Sally Sparrow woman who was in the episode that might've won them over to the show in the first place? At least there's a decent excuse we'll probably never see her again. (And she's definitely NOT Clara.) Likelihood We'll Ever See Her Again:0/10
In a parallel universe where game shows' final jackpots and consequent fortunes depend on knowledge of obscure music trivia and Jon Pertwee/Tom Baker Doctor Who episodes, I've probably gone rich, insane, and am now a powermad despot. But happily we're not there, so I'm actually rather pleasant. Really.