'The Buffybot's Christmas Story'
A Gentleman Of Leisure.
"So how do you know when it's Christmas?" the Buffybot asked.
"I have a very special detection device," said the Doctor. "It activates whenever it's Christmas Day. It doesn't matter where we are - it always knows."
"So how does it work then? Does a buzzer go off or something?"
"No," said the Doctor with a smile. "I bet you'll never guess."
"Hm. A bell, then?"
"Words come up on the monitor screens, saying Merry Christmas, to let you know?"
"No, nothing like that. Nothing noisy, or flashy, or wordy. I told you - you're never going to guess."
The Buffybot looked carefully round the interior of the Tardis for clues. Her eye was eventually caught by something small and shiny standing on top of the central control console.
"Is that it?" she said, picking it up. The Doctor nodded.
"How does it work?"
"Just give it a shake. Gently. If it's Christmas, you'll soon know. It'll tell you."
The Buffybot gingerly inverted it a couple of times and put it down again. A few white particles swirled round the lonely little figure inside. She looked at the Doctor enquiringly.
"Is that all it does?"
"Wait," he said.
Gradually the interior of the Tardis became very cold.
The Doctor smiled, and held out his hand, palm up.
Gently, silently, it began to snow.