Fresh Apples
Peel and cut up an apple and mix it in. Works particularly well with some added Cheddar.
Cinnamon Apples
Peel and cut an apple into cubes; put them in a pan with a little butter, sugar, and cinnamon. Heat them till the apples are a little soft, but not mushy. Add as a topping.
Pears
Peel and cut up a pear and add it in. A traditional take on this would use it in a mac & cheese recipe using blue cheese.