One of the local specialty favourite dishes in Shaanxi province where I am now is Biángbiáng miàn.
Photo by hippietrail
The hanzi character for "biáng" is usually the focus of discusssions of this dish since it takes 58 strokes and is not supported by computers, including Unicode.
But I want to discuss the syllable "biang" in this question. To a beginner in Chinese like myself it seems to be composed of common initial "b", medial "i" and final "ang".
But the Wikipedia article informs me that the alternative names for the dish with more common characters are 彪彪面 (biāobiāo miàn) and 冰冰面 (bīngbīng miàn), which each use a different syllable in place of "biáng" as well as a different hanzi character.
So is this syllable not even possible? If not, which phonological rules does it break? Also if it's not "possible" how could it become popular as part of the name of a dish? Is it something to do with the dialect or accent spoken in Shaanxi?