please note this is largely unorganized ramblings!!!
starbies have a shard, which the keep in a necklace or collar. Without this shard they die. Basically a starbie is formed when a shard of magical space rock impales a helpess animal. Then, that animal will either die or in some cases become a starbie. Usually they lose memories from this experience. the goop of a starbie is determined by what (if any) liquid was near it when it transformed. Starbies can also be born from two starbie parents, goopy would be the same as one of the parents. A starbie x cat would just make a slightly soggy cat.
a (born) starbie starts as an egg, then hatches into a newt. newts are entirely made up of goop and are extremely vulnerable. something could come along and find them sitting in a cup and *sip* no more baby starbie. how tragic. they get less and less goop as they grow up until one day they have only a little patch left, showing that they where once a starbie.