Actually, it is.
2D Games:Just use PNG files with alpha channels for your character.
2.5D Games:Option A: Use "simple" shadows on your character, and have a blurry shadow image.
Option B: Use "flat" or "stencil" shadows on your character, but make your 3DS files and your actor
really small, so that the shadows will be so small in 3D units that filtering will be used on them, and therefore, they will be blurry. (This is an automatic side effect of using Blender for all the 3D stuff.
)