With the FDP at MM, you get 1 large mixed greens salad to share (we were able to substiture a Caesar). You then get 1 flat bread, any vairety, for every 4 people in your party. So even if you only have 5 people in your party you get any 2 flatbreads (lots of food!). You then get your choice of any entree MM offers. Some people have reported getting a "special" menu for Fantasmic, however I think the consensus here was all the usual entrees are on that special menu. They just remove the appetizers as those arent available. As for dessert we have had mixed experiences. We have been offered any dessert on the menu and once we were given a choice of cheese cake, tiramisu or gelato.
So while there is a "set menu", the choices really arent limited. What entrees are you looking at? I know in the past we have had the penne alla vodka, chicken parm, and the steak.
