A couple of times a year, Kopp's offers a special shake flavor, Blue Moon, in its rotating lineup of seasonal tastes. The bright, almost neon-turquoise shake is a regional favorite that most people outside of the upper Midwest have never heard of. No one really knows what the flavor is...Marshmallow? Blue Curacao? I'd say the flavor of this shake most closely resembles a cross between marzipan and Froot Loops.