My girlfriend has found the trick, it works every time, it’s failsafe.
Whenever she wants to take a picture of me she wants me to laugh. But I can’t laugh on command, my face comes out in the most contorted ways, but no smile. ‘Say “cheese”!’ doesn’t work with me either. Same contorsion there.
So instead of saying ‘Say “cheese”!’ she says: ‘Honey…?’ and there’s simply no way, no way whatsoever that I can not smile after she says that.