OK, it's only day 3 and I'm cheating already. This was my idea and therefore I get to play centre forward, or something like that. I'm going to pick an old companion and a new companion.
From classic Doctor Who there can be only one, and yes it is the obvious choice, and I know I am partially choosing her because of the emotional effect of her recent passing. But come on, Elisabeth Sladen as Sarah Jane Smith was the definitive Doctor's companion for so many years. Added to that was the way she bridged the gap from old Who to new Who with the fantastic School Reunion how could I not choose her?
The Runaway Bride and Partners in Crime, but as the series progressed her character changed. She become more vulnerable and more likeable, and she changed the Doctor. It is Donna that we have to thank for bringing the tenth Doctor back down to earth after his Messiah moments in Last of the Time Lords. She helped him do the right thing in The Fires of Pompeii. And then there was Turn Left.
Catherine Tate's performance in Turn Left was just about my favourite thing from the fourth season. It is one of the two episodes of new Doctor Who that I keep on my digi-box and watch regularly (the other is Blink). Her increasing terror at the something hiding on her back and her slow realisation that in order to warn the Doctor and to save the universe she must die first was just gripping stuff.
I didn't think it could happen but Donna Noble went from my least favourite companion to the best that the Doctor has had. It was tragic when her memories were wiped and she went back to what she was before. As her grandfather Wilf, played by the magnificent Bernard Cribbins, said to the Doctor "She was better with you." And she was, and so too was the Doctor. My favourite Doctor Who companion of all time is Donna Noble.