Yes, it happened to me that I went to a karaoke place, sang songs in English, of course, because you don't have much choice. One of them was especially fast in one part, so I messed it up a bit, and the comment I received from a person who knew me was 'Oh, it's in English, how come you can't sing it right!', knowing English is not my native tounge.
Sometimes they just assume, even if they know you and where you are from, that you have to be absolutely flawless in English.
Oh, and once also I was told that I was not a lady because of the way I ate my soup, I just came to Japan and I did what anyone from a foreign country would do, keep your bowl on the table, I was given a really bad time by that a**hole, until his girlfriend jumped in and said that's how they do it...
Anyway, I really find annoying some of the things that you can experiece, like hearing you are fat if you are a little bloated that day, or some 'comliments' I heard people get, like you have such a big nose.
Oh, not to mention big boobs, which I kinda found funny, because I got that one quite often, and sadly, it's soooo far from being true, in my case I mean...