Grimace was introduced in 1971 as a large purple McDonaldland character with an uncertain original purpose.
Early versions of Grimace were designed as a mischievous character with multiple arms who was associated with stealing milkshakes. McDonald's later simplified his appearance and changed his personality, turning him into the friendly, childlike companion recognized by most audiences.
That redesign explains why descriptions of Grimace can seem inconsistent. The modern character is usually portrayed as good-natured and enthusiastic about McDonald's food, while the early advertising version was more directly tied to a theft-based gag.
Grimace joined a growing cast that included Ronald McDonald, the Hamburglar, and Mayor McCheese. His broad, simple shape and unusual color made him especially distinctive in McDonaldland advertising, even though the company never gave him a precise real-world species.