In New Orleans, people throw gew-gaws from parade floats. In Cajun Country, they ride from farm to farm, clowning and singing to beg ingredients for a communal gumbo. Louisiana's carnival sweet is the King Cake, a coffee cake frosted in purple, green and gold.
In England, it's pancakes, and the day is called Shrove Tuesday. Just in Louisiana, you could check out Fat Tuesday and the carnival season leading up to it in one different city or town each year for half a century without seeing everything, whether it's a children's parade, a formal ball, or a glittery parade.
Worldwide, hundreds of cities and towns hold a final blowout before the austerities of Lent - or just because.
In Sydney, Australia, it started as a gay rights protest and is now a huge festival celebrating all aspects of gay culture.
In Moscow, Idaho, it started as a foot parade and bar-based fund-raiser for the University of Idaho's art museum and is now a non-parading festival to benefit children's charities.
You can even find it in India - carnival has been celebrated since the 1700s in Goa, a former Portuguese colony.
Cities and towns throughout Europe and all along the US Gulf Coast have Mardi Gras celebrations.
So do Chicago and Vail, Colorado.
Although Mardi Gras has been a state holiday since 1872, the celebration itself arrived only recently in Louisiana's oldest city. Natchitoches, founded in 1714 -- four years before New Orleans -- saw its first Mardi Gras ball about 30 years ago and its first carnival parade in 1999.