Romanadvoratrelundar aka Romana Doctor Who (both versions)
Romana is the only one of the Doctor’s companion who has challenged him intellectually. While Adric was a maths genius, he was, in every other way, inferior to the Doctor. Romana, on the other hand, another Time Lord (or Lady, though that sounds naff), scored a triple first at the Academy on Gallifrey, while the Doctor only just scraped through. Thus, Romana and the Doctor function much more as equals than he does with many of his other companions and she sometimes gets the better of him.
Romana’s two regenerations provide for contrasting beauties – the aristocratic dark Romana and the blonde waifish Romana. In her second form Romana develops a greater sense of humour. Unlike the Doctor’s regenerations, Romana has much greater control over her form and recovery, which could again be seen as a way in which she is superior to the Doctor.
While in various non television forms, Romana has gone on to positions of great authority within the Time Lord world, part of me hopes that she might still be waiting somewhere in E-Space, ready to return to assist the new incarnation of the Doctor along. It would be nice to think that if the Doctor is not the only surviving Time Lord that Romana might be the one to reappear at some time. As has been pointed out, if some of the Daleks survived (and it seems that a plague of them did) surely some Time Lords did as well. Seeing Romana again in a new body or an old one, would be a big treat for those of us brainy girls who found a character to identify with in Doctor Who as youngsters. There is a new plot for you RTD.
Update: Have now watched The End of Time and hoped like hell that the mysterious woman might have indeed been Romana. Apparently, according to pod-cast commentary, this is definitively not so. However, that doesn’t mean the mind cannot be changed….And there was the second TimeLord woman also….It was the whole “I was lost once” bit which made me particularly hopeful. That and the fact she was clearly a TimeLord. Nonetheless, I think Romana is still someone who can reappear sometime in the future.