Mardi Gras is a festive celebration that begins after Epiphany and culminates on Fat Tuesday, leading into Lent, marked by indulgent eating and drinking. Originating in Mobile, Alabama, it features parades, balls, and traditional foods like king cake, which carries a hidden surprise. The most famous celebrations in the U.S. occur in New Orleans, with customs including dancing, wearing masks, and various social events leading up to the festivities.