Here, now, is my Doctor Who Theorum. Ahem.
The Doctor (11th, 12th, or any otherwise thereafter) comes across his younger self... his first self in fact. Yes William Hartnell is long gone and Richard Hurndell wasn't a great portrayal (though close enough was fine)... Current Doctor should meet with 1 before he steals his Sexy TARDIS, this means any actor that vaguely resembles a younger William Hartnell will fit the role.
William Hartnell, pre-Doctor Who |
The Moff has been hinting at explanations, finally bringing up bits from the past that RTD never touched - such as the theft of the TARDIS, and mention of the Doctor's name!
Along with this is the possibility of including Susan, either with the Current Doctor, or with younger 1.
Finding Susan for the Current Doctor would be an important story - it would answer the important question of what happened to her during the Time War - does being Gallifreyan but living on Earth count in the result of what the Doctor did to stop Daleks and Time Lords alike?
Also meeting Susan again could serve as a catalyst for returning to his own past. Perhaps in some complicated way the Doctor has to cause himself to rebel, maybe doing it so that he doesn't find out who he is...
Susan could be played by anyone really, of any mature age... but it would be fantastic to see Carole Ann ford back, she is in her 70's currently, so maybe not possible. We can but dream!