I understand that taco pizza is really big in the Janesville/Beloit area. The taco pizza I had there was made with ranch dressing (which they seem to put on everything in Janesville), bean dip, nacho flavored Doritos and orange cheese. I don't know if that is a traditional South Central Wisconsin variation, since I only ate it once (never again).
Here is a link to a menu from Mac's Pizza Shack in Janesville where they make some of the weirdest Pizzas I have seen, including Mac n' Cheese and Baked Potato (mashed potatoes, bacon bits, onions, orange cheese and sour cream)
I got a kick out of their "Garden Pizza" which contains salami, peperoni, sausage, ground beef and Canadian bacon in addition to green peppers, mushrooms and onions.
http://macspizzashack.com/menu.html