The Doctor wants to make Sherlock's dream come true

Dean meets the Doctor and each time he is shocked by the change in his appearance

"The only thing that gave him some relief was feeling Sam's thumbs press into the skin beneath his lungs one last time. You've always been my home, Sammy."

"Two thousand and fourteen. If I was in two thousand and fourteen, I did not remember anything of what had happened in the last six months or so. The blow on the head really made me lose my memory. However, I knew what was the scenario that loomed in front of me. The fucking apocalypse."

Sam and Dean found themselves looking around in an old ruin, and the conversation took an unexpected turn.