Despite its blue hue, Blue Moon ice cream tastes neither like the ocean, nor the sky. The Midwestern favorite is, however, equally hard to conceptualize. Several purveyors sell the flavor, but each one keeps their proprietary blend a secret. Speculators are left to their imaginations, which inevitably run wild. The sugar likely doesn’t help.

Some swear it’s almond extract, while others taste citrus. Cereal fans are also divided, mostly between Trix, Froot Loops, and Fruity Pebbles. Still, others suspect the key ingredient must be marshmallows—unless, of course, it’s actually the beaver musk additive known as castoreum. 

No individual has taken responsibility for Blue Moon’s inception, but sources accredit Bill “Doc” Sidon with the invention of the secret formula. The Austrian chemist got his doctorate before fleeing the Nazis with his wife, then became the chief flavor chemist at Milwaukee’s Petran Products in the 1950s. Petran owns the patent to the original Blue Moon recipe.

Those attempting to recreate the cosmic cream at home agree that “Chef #218515” (of the now-defunct Food.com) came closest with a blend of raspberry flavoring, lemon oil, and vanilla pudding mix. Even after the recipe was taken down, other websites republished it. But Blue Moon’s true makeup remains a sweet, enduring mystery. Nonetheless, ice cream parlors continue selling it, both as a stand-alone scoop and as one-third of another iconic, Midwestern flavor known as Superman ice cream.