They always warn you that characters will take on a life of their own.
What started as a simple Betsubetsu Christmas card may well end up being spun-out as a separate entity. The 'Sanuta' character used here is actually derived from a model test rig., and was only pressed into service for the card at the last minute.
The backdrop started out as just 'something green and textured' to hang there in the background. But the lighting accents the specular highlights on the roughness and makes it look rather snow-like. Serendipitously neat, and something to follow up for future investigations...
(Oh yes, and the fur really is Hash 'fur'... giving this scene a very long render time indeed.)