The McDonald's character introduced in 1971 as a mischievous hamburger thief was the Hamburglar.
The Hamburglar was created as part of the McDonaldland cast, a fictional advertising world aimed largely at children. His central joke was simple: he wanted to steal hamburgers, especially McDonald's signature burgers, while the other characters tried to stop or understand him.
The earliest version had a more sinister appearance, including a mask and a ragged costume. McDonald's later redesigned the character to look younger, friendlier, and more cartoon-like. That change reflected a broader effort to make the advertising characters more appealing to families.
The Hamburglar is sometimes confused with Grimace because both were introduced as McDonaldland figures. Their roles were different: the Hamburglar was defined by burger-stealing mischief, while Grimace became a large, friendly purple character associated with shakes and companionship.