hehe i thought this before too i saw too many japanese tourists and chinese citizens in here also i watched too much chinese,korean,japanese movies then i figured it out well you all look same ,small-sized cute little people but ... i think chinese has more yellow skin than others also their eyes more pulled and tiny (too sharp) than others . japanese has whiter skins and bigger eyes than others also their eyes are are not pulled much... koreans... well i m not sure about natural looking ones i heard most of them get plastic surgery from their eyes and faces . they look like japanese a little bit also they look sharp both three nations have bad food tastes :D i could tell you more but its enaugh i guess i hope my friends and people around here wont gonna kill me :P

Japanese spoken language is easier than chinese I believe. (Chinese looks like is 'sang' rather than spoken, while nihongo is more 'rounder'). I don't know too much about korean though. Also, you'll never hear a japanese speaking the termination "ing" ( only "in") or hear the letter "L" when speaking nihongo. Words in japanese are longer than they are in chinese. (There aren't long words in chinese, right? Most of them are one or two syllables).

yes, koreans have the roundest eyes of the three, japanese are the whitest, and chinese have the smallest eyes

Very Very Easy ...

When Chinese and Japanese people speak English it's kinda easy to differentiate between the two. Not too sure about Korean vs. Japanese accents in English though. Then again, I think Korean and Japanese sounds are closer together than Japanese and Chinese. As for faces, I usually know if someone's Korean, Japanese or Chinese but I wouldn't bet on it.