I was glad my father was an eye-smiler. It meant he never gave me a fake smile, because it's impossible to make your eyes twinkle if you aren't feeling twinkly yourself. A mouth-smile is different. You can fake a mouth-smile any time you want, simply by moving your lips. I've also learned that a real mouth-smile always has an eye-smile to go with it, so watch out, I say, when someone smiles at you with his mouth but the eyes stay the same. It's sure to be bogus.
Roald DahlThe walls were wet and sticky, and peach juice was dripping from the ceiling. James opened his mouth and caught some of it on his tongue. It tasted delicious.
Roald DahlThen suddenly, he was struck by a powerful but simple little truth, and it was this: that English grammar is governed by rules that are almost mathematical in their strictness!
Roald Dahl