Answer:
What gets whiter the dirtier that it gets?
It get wetter and wetter the more it dries
They say each one is totally unique
You give it to your daddy, you give to your mommy, you give it to your sister and your brother and even give it to Fido and Lassie. If they give it back to you, then you both have one. You also have an unlimited supply. What is it?
They're big and blue, and larger than seas
Those with eyes bigger than their stomach will definitely leave the restaurant with one of them. It is named after a house pet as well.