"As for him being Asian in MK2 and Caucasian in MK3, they just chose an American actor to play him in MK3, and after that they just stuck to the look."

Actually, they just superimposed the asian face on sub's body in MKII. You can tell because the face and the arms aren't the same color, and also in Sub's versus and profile pics, he's caucasian.

On a separate note, Shang Tsung went from being a little asian guy in MKII to being a bigass ripped white guy whering a coon-skin hat because he can shape-shift.

I think it all has to do with actor availability doesn't it? That Dr. Philip Ahn was probably too busy with patients to deal with MK...Ha!!

Anyways, IMO there really is no hard logistics for the addition of Sub Zero in UMK#...AND Ermac AND Reptile for that matter.

It was all due to popular demand...and the outcry of a sans Sub-Zero/Scorpion MK