The place I study, The University of Auckland, has a considerable Asian population. Though they appear very similar, almost very similar, After I've dome some research these 6 months in Auckland, I've come up with few observations. It's easy to identify them by looking at their names.
Typical Chinese names include the likes of Zhang, Zhu, Chan, Wu, Li, Qin, Lin, Wen blah.. blah.. blahh... Typical Korean names include Lee, Choo, Seuk, Sung and so on... Japanese names are quite complicated. But many of them end with shi, aka, uki, iki, aki, eki etc.. But the real challenge is to identify them by their physical appearance. The Koreans for one can be spotted mostly with straight hair falling over their head and wearing glasses with thick frames. I assume it to their fashion statement. Almost 5 of 10 Koreans I see are seen with glasses with thick frames. Chinese guys mostly have their heads groomed into a porcupine back. long needle like hair with looks like a person who has just been electrocuted. Japanese are quite hard to distinguish. They are usually found playing super saiyan or ninja gaiden even when they get the shortest access to internet. They appear super-charged while playing games like warcraft or tekken.
But when it comes to similarity, there's jus one thing that comes to my mind.
Asians never brush their teeth. The chinatown always sells toothpaste for the other races :D
