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!
I open wide and tight I shut, Sharp am I and paper-cut fingers too, so do take care, I'm good and bad, so best beware.
What is yellow, looks like the moon and has seeds?
What dress does everyone have, but no one wears?
They belong to me; they belong to you; They can make you feel happy or make you feel blue; They never end until the day you do.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?