Designer/artist Tim Simpson's Smile Helmet mechanically draws the corners of your mouth back into a grin. He created it for "people in jobs which demand an unusual amount of smiling, such as air-stewards, receptionists and politicians."
This is the fourth smiling mechanism I've heard of. First, there is paint (ala Little Drummer Boy). Then, there's Vaseline on the teeth. Beauty contestants use this approach. I guess the yucky feeling prompts them to keep their lips off their teeth. The third mechanism is beer.
I like option three.
