Yes! But it depends on where you are staying or dining. There are only certain Deluxe resorts that are equipped with bakeries that can make fancy, fondant-covered cakes.
All the info is in the first post of the
Cake Chatter thread on the Restaurants board, but basically only the Grand Floridian, Yacht & Beach Club, BoardWalk Inn and Contemporary do wedding cake replicas. Animal Kingdom Lodge *may* be able to do it (people have had mixed results with their cakes). If you're staying at the Poly or Wilderness Lodge, you can call Private Dining at the Contemporary and see if they'll make a cake for you and send it over to your resort.
If you're staying anywhere else, your best bet is to have the cake delivered to a restaurant at one of the aforementioned Deluxe resorts. For that, you can call the Cake Hotline (listed on that thread I linked to) or Private Dining at the resort.
I know this sounds complicated, but WDW is a huge place, and they still don't have a very coordinated system for getting anything other than the standard supermarket-style cakes available at the podium of Disney restaurants.