Here are a few things you might now know about McDonald's Shamrock Shake. It has a bigger history then you know. Pretty interesting stuff for a mint green milk shake.
Shamrock Shakes were discontinued nationally in the early ‘90s. Its cult following and huge Internet presence led to it being re-introduced in the late-‘00s
In 1978 We met the Irish Uncle of Grimace Uncle O'Grimacey who promoted the shakes but he was quickly phased out in the 80's.
McDonald's introduced the Shamrock Sundae in 1980.
Harold Rosen, a McDonald's franchisee owner in Enfield, Connecticut, claimed to have invented the shake in 1966. The McDonald’s Corporation has disputed Rosen's claim.