Welcome aboard, Eean! Congratulations on booking your very first cruise with Disney Cruise Line! I still remember my family's first
Disney Cruise Line voyage! It was so magical, as are all of the rest of our cruises with Disney, but that first sailing holds such a special spot in my heart! You're going to have an amazing vacation as there really is
something for everyone in your family onboard!
The exchange you're asking about is called a Fish Extender Exchange. This is not sponsored by Disney Cruise Line, but is a gift exchange that some guests set up in online Disney fan forums where they chat before setting sail. Outside each stateroom on Disney's ships there is a little clip on the wall by the door. These clips are shaped like fish (or starfish, seahorses, etc..). Guests in this exchange will make a hanging pocket that they clip onto the fish clip, thus "extending" the fish: a Fish Extender. These pockets are where they'll leave little gifts for each other.
Disboards.com is one Disney fan site where guests can search the Disney Cruise Forums for their exact sail date and join a chat with other guests on that same sailing. If those guests choose to set up a Fish Extender Exchange they'll do so there. So, pop over to that site and see if one is started for your sailing. My family and I have participated in quite a few of these, and it is a lot of fun to get to know some others before setting sail, meet up onboard the ship, and enjoy exchanging little gifts. My kids love running back to our stateroom to see if there is anything waiting in the Fish Extender, and they adore finding the staterooms of those in our group to leave our gifts!
I hope those details help as you begin to plan your first cruise, Eean! Please stop back if we can help with other questions before you set sail!
Marcy