December 14: "Mycroft Saves the Day" (from Ennui Enigma)
"If you have come to ask me to exert my influence over foreign dignitaries, the answer is no," said Mycroft firmly.
"No, no, nothing of that sort," Sherlock replied, shrugging out of his coat.
"Well then," Mycroft leaned back in his chair and crossed his arms. "Have you come to ask if I will dress as Father Christmas again? That was a one time occurrence, under very particular circumstances."
"Again, wrong," Sherlock replied. "Dear brother, you are becoming rather slow in your old age."
"Piffle," Mycroft replied. "Fifty-five is practically the flower of youth these days."
Sherlock only laughed. "I had an idea for Watson for Christmas, but I need your help to accomplish it."
Mycroft thought for a moment. Normally, he would be wholly unwilling to participate in any such scheme. Years ago, he had been baffled by the way his little brother had taken to the crippled army medic who agreed to room with him, but as the years went by (especially those three during which Sherlock was "dead"), he had come to know and appreciate Watson as well.
"Of course," Mycroft replied.