In Britain, the Twelfth Night Cake was like what we now call Christmas cake, a luxurious special cake laden with fruit and spices.
There would also be a dried bean and a dried pea in the cake. The man who found the bean would be the King of Twelfth Night festivities; the woman who found the pea, Queen. If a woman found the bean, she got to choose the King. If a man found the pea, he got to choose the Queen. They then got to make people at the party do funny things.
Servants were included and got pieces of the cake, too. If they got to be Kings or Queens, even their masters had to obey them, just as was the case with Roman Saturnalia from which Twelfth Night inherited many of its traditions.
By the early 1800s, Twelfth Night Cake was frosted with fancy trimmings and decorated with small figurines made of sugar paste. It died out as a Twelfth Night tradition by the end of the 1800s; being made instead for Christmas and called Christmas cake.
In Italy and New Orleans, Twelfth Night is still considered the start of Carnival season.
In New Orleans, the cake became known as King Cake, and is now made through the Carnival season. The Italians make focaccia bread instead, hiding in it four beans: three white ones for the magi, and one black one. Whoever finds the black one is the master of ceremonies and can choose his Queen.
See also: Galette des rois
Literature & Lore
Now Christmas is past
Twelfth Night is the last
To the Old Year adieu
Great joy to the new!