The Mardi Gras or Carnival season officially begins on January 6th or the "Twelfth Night," also known to Christians as the "Epiphany." Epiphany comes from a Greek word that means "to show." Jesus first showed himself to the three wisemen and to the world on this day. As a symbol of this Holy Day, a tiny plastic baby is placed inside each King Cake.
The King Cake tradition is thought to have been brought to New Orleans from France in 1870. A King Cake is an oval-shaped bakery delicacy, crossed between a coffee cake and a French pastry that is as rich in history as it is in flavor. It's decorated in royal colors of PURPLE which signifies "Justice," GREEN for "Faith," and GOLD for "Power." These colors were chosen to resemble a jeweled crown honoring the Wise Men who visited the Christ Child on Epiphany. In the past such things as coins, beans, pecans, or peas were also hidden in each King Cake.
Today, a tiny plastic baby is the common prize. At a party, the King Cake is sliced and served. Each person looks to see if their piece contains the "baby." If so, then that person is named "King" for a day and bound by custom to host the next party and provide the King Cake.
Mardi Gras Day has a moveable date and may occur on any Tuesday from February 3rd to March 9th. It is always the day before Ash Wednesday, and always falls 46 days before Easter.