McDonald's fictional character setting was called McDonaldland.
McDonaldland was introduced in the early 1970s as a fantasy world populated by advertising characters such as Ronald McDonald, the Hamburglar, Grimace, and Mayor McCheese. The setting gave McDonald's a connected story world rather than a collection of unrelated mascots.
The campaign was designed especially to appeal to children and helped make the restaurant's branding more theatrical and memorable. Its characters appeared in television commercials, restaurant promotions, packaging, and other marketing materials.
McDonaldland is sometimes confused with individual characters or with the name of a promotional play area. It refers to the fictional world itself, while characters such as Grimace and the Hamburglar are inhabitants of that world.