The shelf being referred to here is the back of your refrigerator shelf where you scrounge around and find an ancient bottle of margarita mix from Cinco de Mayo circa 2009. You then reach in and find a can of your husband's Busch light- hey we're all on a budget, right?
Put them together and what do you get? Wait for it....
Busch-light-a-rita! Ta-Da! Delicious AND low calorie, it is a win-win folks.