Amy Pond knew all about Rose Tyler.

Sometimes, when the Doctor would get in one of his moods, when that terrible look of complete and utter misery came onto his face, and Amy knew he must be thinking about all of the people he had lost in his long, long life, he refused to speak a word about his past to Amy, or Rory, or anyone, really. He would lock himself in his room, not eating, not drinking, just staring at the wall, the ghosts of the people he had loved floating before his eyes. Those days, it was all Amy could do to bring him some food and try to convince him to eat it, and just sit next to him and hold his hand so he wouldn't have to be alone with his memories.

Sometimes, however, when the Doctor got like that, all he wanted to do was talk. He would get Rory and Amy and tell them about all his past companions, of all the adventures they went on together. Sometimes he would say things that didn't make sense to anyone but him, over and over, as he drowned in an ocean of guilt and misery. Sometimes, the stuff he said actually made sense. He would talk about the places he had gone with his past companions, the things they had seen, but mostly he just talked about them. He talked about every detail of them and their personalities until Amy and Rory felt as if they knew them as well and he did. He talked about Susan and Martha and Donna. How brave they were, how clever they were, of all the extraordinary things they had done.

Mostly, though, he talked about Rose. How after the Time War, when he had lost all hope, she had taught him that life could be good again. How she made him feel like he wasn't alone in the universe anymore, how, standing by her side, he felt happy in a way he hadn't in the longest time. He told them every little detail about her, from her favorite color to her middle name. All the time he talked, tears would be sliding down his face, and his voice kept cracking, and loss in his eyes grew greater and greater until he couldn't stand it anymore and he had to think about something else, immediately, to stop himself from breaking into a hundred million pieces that Amy and Rory wouldn't be able to put back together no matter how hard they tried.

Sometimes he told the same stories over and over again, until Amy and Rory could recite information about Rose Tyler like an encyclopedia. It made them better at noticing things. Little things, like how certain words or sentences could drag the Doctor back, and for a moment, unfathomable grief would flood his eyes. How there were certain rooms on the TARDIS that were always locked, but they would occasionally see the Doctor enter them, and when he emerged his face would be wet with tears. That though sometimes the Doctor just seemed like a regular, goofy man, he was a 1200 year old Time Lord that had experienced loss that Amy and Rory could never understand. It reminded them that the Doctor was the last of his species, and every human he ever loved would die.

And there was nothing Amy could do about it. For when you had lived that long, and lost that much, there was nothing a human could say or do to comfort you.