Pies and cakes should be cut neatly, in even wedges or slices. Anything eaten in front of the TV has no calories. This may have something to do with radiation leakage, which negates not only the calories in the food but also all recollection of having eaten it. Entire no-calorie dinners are now manufactured and frozen for this purpose. If you have a drink in your right hand, anything eaten with the other hand has no calories.
Several principles are at work here.
I'm not exactly sure how it works, but it's reversible if you're left-handed. Girl Scout cookies, bake sale cookies, ice cream socials and church strawberry festivals all have a religious dispensation from calories. It's in the Bible. Not only is it unnecessary to decline, it's impolite. Sausages, cocktail franks, cheese and the like are all fattening unless impaled on frilled toothpicks.