As its name suggests, the Grimace Shake is inspired by Grimace: the anthropomorphic purple blob that may or may not be a giant taste bud. “Our fans have amazing childhood memories of their birthdays at McDonald’s … and Grimace’s Birthday is all about paying homage to the amazing, fun moments we all share,” Tariq Hassan, chief marketing and customer experience officer at McDonald’s USA, said in a press release. The Grimace Shake and the rest of the Grimace Birthday Meal will be available at participating restaurants in the U.S. starting Monday, June 12, and only while supplies last.