• Harold Rosen, a McDonalds franchisee in Enfield, Connecticut with a background in "dairy manufacturing," claimed to have invented the product in 1966 with help from a friend named "Bridie Flannery."
• The McDonald’s corporation disputes Rosen's claim. It says the Shamrock Shake was introduced in 1970 and will not comment on any history prior to that.
• Over 60 million Shamrock shakes (one and quarter billion ounces) have been sold since the "official" launch 1970.
• In 1975, the restaurant chain rolled out an obese green character named Uncle O’Grimacey to promote the shakes. According to corporate myth-making, O’Grimeacy resided in Ireland, but took “his annual vacation to McDonaldland around St. Patrick's Day” to visit his nephew Grimace.
• O’Grimacey mysteriously disappeared shortly thereafter, though remains a hero for a small cultish group of internet idolaters.
• A 32-ounce "large" Shamrock shake contains 1160 calories and 88 percent of the USDA’s recommended daily allowance of saturated fat.
• McDonald’s Restaurants of Ireland, Ltd, describes the product as "a unique food for Ireland," overlooking its American origins.
• The Shamrock is the only McDonald's shake whose name does not identify the flavor. According to Rosen, “It’s mysterious.”
Sources: Hartford Courant, The Daily Press (Newport News, VA), McDonalds.com