My next-door neighbor, who is 84 and has lived in Sun Prairie all her life, recommended this place for breakfast. It has some very kitschy decor (basic small-town breakfast restaurant style) with lots of gingham and wooden chickens, but I didn't care.
Nothing on the menu looked very exciting, and it seemed like everything cost a dollar or two more than I would have expected. But the waitress was extremely nice, the coffee was good, and the food (I got the mushroom and cheese omelet) was great. My omelet had three (3!) kinds of cheese and lots of nice 'shrooms inside. It was terrific and also came with hash browns and my choice of toast/pancakes/muffin. I got the rye toast, as always.
We got there around 8:30am (on a weekday) and almost had the place to ourselves but more people kept trickling in as we ate.