Say Cheese: Colloquial. Expression used by photographers to elicit smiles in their targets. When you say the word, the cheeks tend to lift, the corners of the mouth tend to turn up, and the teeth tend to show.

C'mon, Channing: You got a nice photo-spread in Vogue, man. Show some teeth. You should be happy. Smile, goddamnit. Smile! When the photographer asks you to say "Cheese," say it, motherfucker.