Every stateroom has a fish hanging on the wall outside the door. This is part decoration and part message center. The fish is there for Disney to place important communications to you such as excursion tickets and notes from the Cruise staff. It is like a mailbox for your room.
On the DISboards discussion forums, it is very popular to participate in a Fish Extender exchange. This entails having a fish extender hanging off the fish outside your room.
All the people in the exchange buy little items and place them in each other’s fish extenders. It is great fun to come back and check the items you have received.
You can get a custom fish extender made just for your family from the kimtown shop!