unitled: Apparently, showing characters with only 4 fingers is insulting in Japan; it is a common injury sustained by meat workers, and inferring that's one someone does is a slur on their social standing. So, when the first game was released over there, they edited the game to have 3 fingered Mudokens, which then stuck.
I seem to remember they had to make some other changes regarding some severed body parts in the intro sequence, but I can't remember exactly what they were :S