Cheese is the cheese on the mousetrap. I found recently here Cheese On The Mousetrap that there is a certain kind of demon that exists in us. It has a coyish nature, loves sex, and attention.
The facial expressions this kind of demon makes in your wife:
Did you really buy this for me? Oh I am soo excited!
Look at the hands. That pose is the demon pose:
Just coy as can be.