Barnable

 was a boy who lived in the town of Christmas on the planet Trenzalore three hundred years after the arrival of the Doctor. He was a close friend of the Doctor and believed in him. When a wooden Cyberman arrived three hundred years after the Doctor first started protecting Trenzalore, he alerted the elderly Doctor and watched as he destroyed the Cyberman. Barnable thanked the Doctor for fixing his father's barn and asked him why it was now bigger on the inside, but the Doctor asked him to keep it secret. When the TARDIS returned and the Doctor started to leave for the Papal Mainframe, Barnable hid himself behind the TARDIS and sadly asked the Doctor if he was leaving for good now. When the Doctor told him he would return, Barnable promised to wait for him. Barnable was still waiting when the Doctor returned some time later.

What appeared to be centuries later, the now frail Doctor believed that Clara was the presumably-long dead Barnable when she arrived and later asked another young man if he was Barnable, showing signs of senility and his fondness for the boy in still remembering him in that state. The young man said no, but the Doctor called him Barnable anyway. (TV: The Time of the Doctor)