What does this poster mean?

-Around town, i have noticed that there are posters that say "Give us a smile" - like this one - http://www.google.co.uk/imgres?imgurl=ht鈥?/a>



I was wondering what do the posters actually mean and what is the M.G?



ThanksM G stands for Myasthenia Gravis, a condition which affects the muscles. Sufferers are unable to smile, hence the slogan on the poster.
M G was the name of the person who started the charity