Grimace was originally associated with stealing milkshakes.
When Grimace first appeared in McDonald's advertising, he had four arms and was described as a villain who took milkshakes. This early version was notably different from the large, purple, friendly character most people recognize today.
McDonald's later redesigned Grimace with a simpler shape and a more harmless personality. The change made him better suited to the friendly McDonaldland ensemble, alongside Ronald McDonald, the Hamburglar, Birdie, and Mayor McCheese.
The character's later identity became less about a specific food-related crime and more about companionship, playfulness, and his distinctive purple appearance. That evolution is why older descriptions of Grimace can sound surprising to audiences familiar only with the modern version.