Ronald McDonald is a clown character used as the primary mascot of the McDonald's fast-food restaurant chain. He inhabits the fictional world of McDonaldland, with his friends Mayor McCheese, the Hamburglar, Grimace, Birdie the Early Bird and The Fry Kids.
Many people work full-time making appearances as Ronald, visiting children in hospitals and attending regular events. At its height, there may have been as many as 300 full-time clowns at McDonald's restaurants. There are also Ronald McDonald Houses, where parents can stay overnight with their sick children in nearby chronic care facilities.
Source : Wikipedia
