This is a true story that happened to me only a few years ago.   

I'm a 3rd generation Cantonese-American and have pretty much forgotten the language. Hey, I wasn't even raised with it spoken in my household, but I live in a predominantly Asian neighborhood anyway.

Well, Mormons, whom we all know and love (cough), have to save their money during childhood so that they may go on missionary expeditions when they hit seventeen years of age or so. Some even become Urban Mormons, where they trek to distant (?) parts of Suburbia, seeking converts. 

So, one day, there was a knock at my door. So upon answering, Lo and Behold! Who should be standing there, but two young, aspiring Jehovah's Witn--I mean, Mormon Missionaries. Both were Caucasian, and one was holding a copy of Halston's Mandarin/English Dictionary. The Mormon holding the dictionary greeted me in a foreign language, presumably Mandarin, which I didn't understand. However, I chose to say nothing; I merely furrowed my brow and intensified my gaze.

Astute, as they were, the missionaries were quick to realize that I had not comprehended a single word they said, so they squabbled:  

Missionary #1: I told you he wasn't Mandarin. 

Missionary #2: Apparently not. He's probably wondering what  we're trying to say.

Missionary #1: Maybe he's Vietnamese. 

Missionary #2: (Pulls out Vietnamese/English Dictionary) Perhaps.  The Word of God was meant to reach all tongues.  

So the second Missionary repeated his greeting in Vietnamese. I only shrugged my shoulders.

The other Mormon pulled out a Japanese Dictionary, assuming that I might have been the same.

Again, I merely shrugged, and we ran the same gauntlet for the Korean language.

I had to admit, though, that I began to tire of this game. Taking a deep breath, I shouted,   "YOU DAMN FOREIGNERS! WHY DON'T YOU GO BACK WHERE YOU CAME FROM AND STOP TAKING OUR JOBS?!?"  

With that, I slammed the door in a grandiose fashion and couldn't stop laughing for two hours afterward.