You will end up with asterina stars on your own. When you buy frags, you will be 99% sure that you will get some of these with your coral. You can't hardly kill them.
The brittles are cool. I have got a lot of those in both of my reefs, they are just buried in the rocks, so all you see are the legs. Also have a huge number of speghetti worms in my little reef. They are pretty cool as well.