Officer Big Mac was the McDonaldland character introduced as a police officer who protected McDonald's food.
The character was designed as a law-enforcement figure with a head modeled on a Big Mac hamburger. This made Officer Big Mac part of the same visual system as Mayor McCheese and other food-based McDonaldland characters.
His role gave the fictional setting a recognizable authority figure and created a natural counterpart to characters associated with stealing food, especially the Hamburglar. The conflict was playful advertising rather than serious storytelling.
Officer Big Mac is sometimes mistaken for Mayor McCheese because both represented civic roles. Their titles distinguish them: Mayor McCheese was the town's political leader, while Officer Big Mac was its police officer.