Outside every stateroom, there is a little decorative fish which holds notes and messages. It is also from here that hangs the fish extender. Fish extenders are pocket organizers, with pockets for each member participating, to hold little gifts from other guests. Kind of like a Secret Santa.
Basically, you join the FE group for your cruise. This list is cut off about a month prior to your sailing, so you have enough time to prepare for all the people on your list. You can find your FE group either on Facebook or on the Dis Boards.
I made a basic FE using an organizer from Ikea and used some paint to decorate. It was very amateur compared to others. Others had amazing ones done with their names stitched on, along with their favourite characters.
Q had so much fun checking the FE everyday, getting so excited with every gift. This is just a few of the gifts we received.