Donut Burger?

In the neverending race for profits and new market niches, the master of incongruous mix 'n match, Mos Burger, has come out with a ... Donut Burger! Here is a good picture in another blog (although blog entry incorrectly says Mr. Donut) Why not? As some will fondly remember, White Castle burgers were square with a few holes... I think we used to call them "sliders" in college.