Grimace was introduced by McDonald's in 1971.
The character first appeared as part of the McDonaldland advertising universe. Early versions of Grimace were portrayed differently from the friendly purple character familiar today: the original design had four arms and was associated with stealing milkshakes. McDonald's later simplified the design and changed Grimace's personality.
The revised Grimace became a large, purple, childlike companion of Ronald McDonald. His appearance and limited dialogue made him visually distinctive, while his role shifted from a mischievous product-related figure to a friendly member of the McDonaldland cast.
The introduction date is sometimes confused with the character's redesign. 1971 identifies Grimace's debut, not the later point when the familiar one-piece purple form became standard. The character remained part of McDonald's branding for decades and experienced renewed public attention through later social-media campaigns and merchandise.