Grimace was originally designed with four arms when the McDonald's character debuted.
Early versions of Grimace looked different from the friendly purple character familiar from later McDonald's advertising. The original design included four arms and was associated with the idea of stealing milkshakes. McDonald's subsequently simplified the character's appearance and changed the role into a more amiable companion for Ronald McDonald and the other McDonaldland figures.
This evolution illustrates how branded mascots can change as a company adjusts its advertising for families. The later Grimace was presented as a large, purple, good-natured figure rather than a threatening or mischievous product thief. His visual simplification made him easier to recognize across television, packaging, toys, and restaurant materials.
The four-arm detail refers to the character's early design, not to the modern version. It is also separate from the Hamburglar's defining role as a hamburger thief. Grimace's redesign helped establish the character's enduring place in McDonald's branding.