The last day before the beginning of Lent on the Gulf Coast that once belonged to France, it is Mardi Gras, "Fat Tuesday": Laissez les bon temps roulez!
It was first celebrated in Mobile, Alabama, but the big show these days is in New Orleans, and it is a holiday in the state of Louisiana, because people wouldn't show up for work anyway, so why fight it.
The tradition is to serve King cake, which is a circle of cinnamon bun dough with a white frosting on top sprinkled with sugar colored purple, green, and gold. If that weren't bad enough, they put the figurine of a baby in the dough, and whoever finds it in their piece is supposed to be lucky. Actually if you find it and don't choke on it, I guess you are lucky. You should use a small ceramic figurine, as some of the cheap plastic versions melt in the oven [yummy].