The cheese-headed mayor introduced in McDonald's advertising in 1971 was Mayor McCheese.
Mayor McCheese was one of the original characters in McDonaldland, the fantasy setting McDonald's created for its advertising. He had a large cheeseburger-like head, a mayoral sash, and formal clothing, making him a walking visual pun on the chain's signature food.
The character appeared alongside figures such as Ronald McDonald, Grimace, the Hamburglar, and Captain Crook. McDonaldland gave McDonald's advertising a connected cast and a recognizable fictional setting aimed especially at children.
Mayor McCheese is sometimes confused with Officer Big Mac because both were anthropomorphic food-based characters in the same advertising world. Mayor McCheese was the mayor; Officer Big Mac served a different role and had a Big Mac-shaped head.