For many, St. Patty’s Day is about Guinness, Bailey’s and Jameson, but let’s not forget that other important Irish Day drink, the Shamrock Shake. Sure, a large is loaded with as many calories as 1 and a half Big Macs (820 calories), but after more than 45 years, it’s earned its part in the national St. Patrick’s Day celebration. Here are 7 things you never knew about the iconic McDonald’s seasonal green shake. 1. The first shake was introduced in 1970. It was originally called the St. Patrick’s Day Shake, but was scrapped years later for something a little more creative — the Shamrock Shake. 2. Shamrock Shakes were a charitable endeavor What do Shamrock Shakes have to do with the Philadelphia Eagles and St. Christopher’s Hospital for Children? In 1974 after watching his 3-year-old daughter undergo treatment for leukemia, Philadelphia Eagle Fred Hill reached out to the community to raise money for…