Well, It has not been done in the past five generations because of the complexity (and extreme difficulty) of morphing 2 completely different models into one another. Other than masking it with a shitload of smoke or something to that extent, having a morph is not very easy. Take Liu-Kangs Dragon fatality that was done in 3D for Mortal Kombat 4 and in Mortal Kombat: Shaolin Monks for example: it had to be masked with smoke, because the morphing is not easy to do as an actual animation. (I am a 3D modeler/animator; I know what im talking about, as I've tried to do this on many occasions for a redone version of Scorpions Mortal Kombat 4 fatality where he morphs into a giant scorpion) Usually, the biggest problem faced when making the animation where the model is to morph from one model to another is the screwyness of the joints, just sporatically moving about, greatly changing position, etc. On top of that issue, there is the problem of creating brand-new geometry and adding it to the model's existing geometry. Now, this would not be too big of a problem if there was unlimited memory for the console, but having every single character model as a part of the base model would put the poly-count through the roof for the character, and well, in any game, that is very much an undesirable thing, as it leads to huge performance issues. Granted, that most likely would not be such an issue on the PS3 and probably not too bad on the 360, but the wii would not be able to handle it at all. But, even so, there is still the issue of loading the other character (this is assuming that you go with the whole "smoke concealment" method). In Mortal Kombat Trilogy for the PS1, using Shang Tsung, and morphing made you, and the other player quite angry, as due to memory limitations, only 4 total characters were able to be loaded at one time. When Shang morphed, the game actually had to load all the sprites, controls, and sounds for the character he morphed into, right on the spot. this caused a 1-2 second span of no movement or action at all, as the game was loading. Granted, we have more RAM in consoles now, but still, either all characters would have to always be loaded when using the morphing character, or the game would have to pause momentarily for the character to be loaded. Morphing is not a problem in Fatalities, because the game is able to do the 'starting' animations for the Fatality whilst loading the new model, not causing any pause in action.
