The Shamrock Shake is a seasonal dessert sold at select McDonald’s fast-food restaraunts during March, to celebrate St. Patrick’s Day. Essentially, the Shamrock Shake is a standard vanilla shake, flavored with mint extract and dyed green.

Shamrock Shakes were widely available across Canada and the United States until the early 1990s. According to the McDonald’s website, Shamrock Shakes are now sold exclusively in Ireland, although they are still available at select American stores during the month of March. The Shamrock Shake typically appears in mid-February.

During the 1980s, McDonald’s used the Uncle O’Grimacey character to market Shamrock Shakes. However, he has been phased out, but is said to return along with Grimace and Mayor McCheese in a series of television spots on Nickelodeon starting in 2008.

In 2008, McDonald's Canada brought back the Shamrock Shake for a limited time only starting on February 26.