Fisheaters has everything you need to know about Twelfth Night, including a poem by Robert Herrick:
Twelfth Night: Or King and QueenShare
Now, now the mirth comes
With the cake full of plums,
Where bean's the king of the sport here;
Beside we must know,
The pea also
Must revel, as queen, in the court here.
Begin then to choose,
This night as ye use,
Who shall for the present delight here,
Be a king by the lot,
And who shall not
Be Twelfth-day queen for the night here.