The McDonald's character known for stealing hamburgers and wearing a striped disguise was the Hamburglar.
The Hamburglar was one of the central characters in McDonaldland, the fictional universe used in McDonald's advertising. His defining behavior was attempting to take hamburgers, creating a simple comic conflict that could be understood quickly by children.
The character's appearance changed over time. The earliest version was more like a small, elderly trickster, while the later redesign presented a younger figure in a striped outfit and cape. Despite those changes, the hamburger-stealing theme remained the character's central brand trait.
The Hamburglar appeared alongside Ronald McDonald, Grimace, Mayor McCheese, and other advertising characters. He is not the same figure as Captain Crook, who was associated with Filet-O-Fish promotions and had a different visual identity.