I know that bent pony legs and horns can be fixed with application of heat. You could try dunking the piece in boiled water or running it under a hair dryer for a few minutes, then taking it while still hot, bending it the way you want it to and clipping it into place. Bent ponies are small enough to be put into the freezer to set the shape but the castle is a bit big for that, it should be alright if you just left it to cool down at room temperature though.