Bill, who had a rough time towards the end of the season, what with being turned into a Cyberman. But she got better (sort of), so it all worked out in the end.
I was pretty excited by the final scene. The 12th Doctor was fighting his regeneration, preferring to die. He was then approached by another version of the Doctor. The Original Doctor!
The original actor who played the Doctor, William Hartnell, died way back in 1975. So the character has been recast with David Bradley, known for his work in "Game of Thrones" and "Harry Potter" movies. The two Doctors will team up in the upcoming Christmas episode, where Capaldi will pass the torch to some other actor.