On our most recent trip (Feb 2006), Yacht Club Galley had a dessert that was several white chocolate pieces shaped like puzzle pieces that you can put together and then paint with icing. It is also served with a cupcake. My kids enjoyed putting the puzzle together (when put together, a Disney character appears; in our case, it was Tinkerbell) and painting it, but they did not eat much of the dessert, instead preferring the cupcake that was served with the dessert.
I also believe I have had a similar dessert elsewhere on property in the past, but not sure exactly where (I think it was either Artist Point or Citrico's).