Any time there is a lot of snow on a hillside, there's a possibility of snow rollers. This is a natural phenomenon that looks like how you start a snowman by rolling up a bunch of snow. They can sometime form into big wheels, like the snow roller above. They can also look like carpet rolls, or big boulders, or small balls.
Whether or not nature can be anthropomorphized is a matter for debate. However, one’s first reaction is, inevitably that it must have been a person or persons unknown who took the time to gather a handful of snow and then slowly and carefully roll it until it became too large to push anymore. Yet a brief inspection of the snow around reveals no footprints. So how were they created? There is science behind this magical and mysterious apparition.
When the top layer of a thick blanket of snow begins to melt and become heavy on the side of a hill, it might begin to roll o itself. As the glob of snow rolls down the hill, it gathers up the snow beneath it like in the game Katamari Damacy. The effect is quite eerie when you consider it all happening without human intervention. It's not real common, because conditions have to be just right, but there is plenty of photographic evidence at Kuriositas.
(Image credit: Flickr user Washington State Dept of Transportation)