Grimace was originally portrayed as stealing milkshakes in McDonald’s advertising.
When Grimace debuted in 1971, the character had a more mischievous role than the friendly purple figure familiar from later campaigns. Early advertising presented Grimace as a milkshake thief, giving him a simple conflict with Ronald McDonald and the other McDonaldland characters.
McDonald’s later softened and redesigned Grimace. The character became larger, friendlier, and less threatening, eventually being described as a lovable companion rather than a villain. That change is why many people remember Grimace as a cheerful purple mascot and do not associate him with his original advertising role.
Grimace is sometimes confused with the Hamburglar, whose defining gimmick involved hamburgers. The two characters belonged to the same fictional advertising universe, but their early roles centered on different products.