Disclaimer: Property of J.K. Rowling.
Snape was busy preparing potion ingredients when the envelope slid under his office door without warning. Seasonal festivities were all well and good, but there were many spells that could only be performed at midwinter, and he had almost forgotten about Christmas entirely.
It was an entirely mundane muggle card, so there was no speaking, no dancing, no singing of carols. Not even glitter. Snape looked at it as if it was in imminent danger of exploding, even so.
He didn't open it, or risk throwing it away, but slipped it into a pocket and went quietly back to work.
The End