Languages that make you smile

Watching the 21 Accents video (via Neatorama)  made me think that different languages/accents seemed to require different mouth positions. Is it possible that some phonemes are only achievable with the mouth wide-stretched in a smile? Then loading a language with such phonemes would be one way to ensure people appear friendly to strangers whatever the real mood of the person.

Social engineering through accent shaping, now that is an interesting thought!