I don't know exactly what you mean, but didn't Chretien have Bell's Palsy?
"I wrote a song about dental floss but did anyone's teeth get cleaner?" -Frank Zappa
"A thing moderately good is not so good as it ought to be. Moderation in temper is always a virtue, but moderation in principle is always a vice."- Thomas Paine
"I'll let you be in my dream if I can be in yours." -Bob Dylan
It could be the result of a palsy or a stroke or some other neuromuscular disfunction. It could be the result of the two halves of the brain not coordinating. I had a New Wave friend who claimed it was the sign of dishonesty. It could be someone doing that Seinfield voice: "Hellllooooooo, la la la."