Answer:
White fat and fluffy, May even look like a puppy. Seems heavy but is light, Floats about without a worry, But if it turns dark you have to hurry!
A shimmering field that reaches far. Yet it has no tracks, And is crossed without paths.
Look into my face and I'm everybody. Scratch my back and I'm nobody.
This only turns over once you have traveled very far. What is it?
You heard me before, yet you hear me again, then I die. Until you call me again.
It can be cracked, It can be made, It can be told, it can be played. What is it?