One of my best friends in vietnamese. We were walking from the car into a restaurant for lunch and a guy stops us (ignored me completely) and with a huge smile says something I don't understand to my friend and asks him in English if he is Philippino. My friend drops an angry, "no I'm not. What is wrong with you?!!!"
After we are out of earshot of the guy, I say, "wow. I have never seen you that upset. What happened?" He explained that happens all the time with Asians thinking they know what his ancestry is and he thinks it is completely messed up to approach someone that way.
Of course, now whenever I see him I am sure to say something like, "Hey, I met a Korean guy at work who looks EXACTLY like you. Are you sure you aren't Korean?" 🙂