The Society for Creative Anachronism (SCA) is basically the world's biggest costume party, with tens of thousands of members. It is, at the same time:
Everybody dresses up and takes a stage name, which can be confusing. They can even have multiple stage names for different roles. What's more confusing is that the local and regional chapters have stage names, too. So, this isn't the Durham chapter in the Central NC area of the Southeastern division. No, it's the Canton of Buckston upon Eno in the Barony of Windmaster's Hill (an obscure reference to the Wright brothers) in the Kingdom of Atlantia.
A big part of the fun is in the members who put on knightly armor and fight for the honor of their consort. Whoever wins the semi-annual sword and shield tournament gets to be king (or queen, as it sometimes turns out) and preside over the feasts and ceremonial occasions. When an area gets enough members, it can have its own "crown tournament." There are 16 such kingdoms so far.
As in medieval Europe, kings come and go, but the ministers really run things. So, keep in mind that the club officers are not necessarily the ones sitting at the high table with crowns on their heads.