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. 
T.S. Elliot (who wrote the book that Cats was based on) had a more novel
method of dealing with door-to-door missionaries. One day, some Jehovah's
Witnesses showed up on his doorstep with a can and said, "Money for
Jehovah?" To which Elliot responded, "Great! I'm Jehovah! How much
have you gathered for me?" 
They left in a huff.