Actually they can be whatever theme you want, but must contain a hidden mickey within it. Im sure all you pin collectors know what im talking about here. I just think tiki got confused when i explained it to him. The are called Hidden Mickey Series Pins, usually only available to Cast Members but are now being sold in the parks in mystery pouches.
For example: this here is the DLR - 2008 Hidden Mickey Series - Alice In Wonderland Chess Collection (King of Hearts)
http://www.pinpics.com/cgi-bin/pin.c...740.1212515997
There are 6 in the set