Wisconsin's messy contribution to the world of burgers is called butter burger. For some, butter burger is authentic when the ground meat is combined with butter. For others, it's when the bun is buttered, toasted, and topped with some more butter before serving.
The only thing that everyone can agree on is that there must be enough butter to drip off the meat, which will usually form a small pool of butter on one's plate. A theory says that the name comes from a place called Solly's in Glendale, Wisconsin, operating since 1936, where the butter is added to the meat that is, again, fried in butter, and served with a side of stewed onions.