Donna. Mel. Amy. Turlough. What’s with all the redheads on the TARDIS? Greig Byrne at the Doctor Who zine Kasterborous thinks he knows why the Doctor appears to favor companions of the ginger persuasion:
Why has the Doctor expressed such an interest in this “dying breed”? First one must ponder the doomed and tragic fate Gingers face. It’s all down to a recessive gene: it takes two Gingers to make another, or at least two with the Ginger Gene, if not Ginger hair.
I therefore submit that given the Doctor’s belief that he can simply manifest his Gingerosity without said need for the gene pairing (but a mere regeneration) it’s incumbent upon him to repopulate the future-extinct Ginger race.
No, not like that, you perv. Like this:
[Q]uite apart from his protective stewardship they could easily have been subjected to furtive genetic examinations. He probably has a pair of particularly powerful reading glasses that scan DNA.
Is the future of the Ginger race assured with his doting oversight? Or may we assume retrospective success given that Gingers have indeed been here at all? (Hey for all we know we were wiped out already and he brought us back).
Though as a possessor of the ginger gene myself, I would happily volunteer for some like that. Purely for scientific purposes, of course.
(If you stumble across a cool Doctor Who thing, feel free to email me with a link.)