Aziraphale did not believe him. But it was Christmas.

"How clever you are," he said indulgently. "An artist, really."

Then he moved to the window and opened it. A chill came in, but he flicked his hand and the fire roared to life in the fireplace at the same time. He stuck his head out of the window and opened his mouth. Then turned around and showed Crowley an absolutely perfect snowflake stuck to the tip of his tongue.