The
Castaway Club is
DCL's returning cruiser program. You become a member by sailing with them. Since you just sailed in August, you should be receiving your membership materials fairly soon. You can always call them at 1-800-449-3380 to ask when to expect them. Sometimes it takes a month or two for them to process things after you sail.
As far as being worth it, it's free, so in that sense, I guess it is. The benefits aren't really overwhelming. Returning cruisers get a gift in their stateroom. For a while it was a pretty nice sports bag. I think it's currently a beach towel, but I'm not sure. You also get an invitation to the returning cruisers party, which will be held one night on the ship. There are free cocktails and hors d'oeuvres, and the Captain and some of the crew mingle around and talk to you.
There is also a "special" check-in line at the port for club members, but in my experience, there are usually a few of the regular lines which are shorter than this one.
Membership used to also get you a stateroom credit if you booked within a certain amount of time from you previous trip. I believe that you can currently only get this credit if you book on board.
That's about it, I think. Can anyone add to this?