Series 6, Episode 12: 'Closing Time'
"I'm sorry, Alfie, I can't leave you here on your own. There's something up with the Doctor, and we owe him. I wouldn't have you or Mummy if it wasn't for him. He needs someone. He always needs someone. He just can't admit it" In a farewell tour before he dies, the Doctor revisits Craig, who's now married with baby Alfie. The Doctor teaches Craig parenting skills whilst investigating a Cyberman attack in a local department store. It's revealed that it's River who kills the Doctor in Utah.
Series 6, Episode 13: 'The Wedding of River Song'
"Imagine you were dying. Imagine you were afraid and a long way from home and in terrible pain. Just when you thought it couldn't get worse, you looked up and saw the face of the devil himself. Hello, Dalek." All of time and space is happening at once, because River refuses to kill the man she loves and create a fixed point. The Doctor marries her in the alternate timeline, before revealing to her that he's actually inside a Teselecta version of himself. The Doctor escapes, but vows to lie low from now on.
Christmas Special 2011: 'The Doctor, the Widow and the Wardrobe'
"Because every time you see them happy, you remember how sad they're going to be, and it breaks your heart. Because what's the point in them being happy now if they're going to be sad later? The answer is, of course, because they are going to be sad later. Now, we'd better get downstairs. I think they may have found the main sitting room." The Doctor becomes janitor of a country house, looking after a war-time family. When he gets them a trip to a Christmassy forest, he doesn't realise that the planet is about to be harvested, and it's up the mother of the family to save her children, the Doctor and her husband.