Every year I host a 4 part game in my area- I, along with a lucky group, play on Mardi Gras, St. Patrick's Day, April 1st, and conclude on Cinco de Mayo. This game is always anachronistic and breaks the 4th wall with humor on a regular basis. For example, this year the antaganist of the adventure was Al Gore, a mad mage insisting that Golarion would heat up to the point it would combust if he didn't do something about it was attempting to perform a ritual that would plunge the world into an endless Winter, assisted by his flesh golem, Man-Bear-Pig. Upon his defeat the party learned that he was being manipulated by an evil succubus, Hilary Clinton, and needed to put an end to her vile schemes. Every player strives to come up with the most mechanically sound, but rediculous character imaginable, be it through pop culture references or other inanity. Obviously the jokes are bad, and that is the point, see this year's plot above. Then every character is given quirk which they must follow, assigned via being drawn from a hat with recomendations from all included. This year our group's fighter could only speak if he included a bad pun, for example. Then we turn the adventure into a drinking game, which the rules change for year to year but have the same premise, of certain actions or saying certain words or certain die rolls force drinks. By the end of each night of "Drunk D&D" the players are so intoxicated that their in-character actions and impersonations are frankly as halarious as they are absurd, and we get to see some crazy choices and risks that would never happen in a normal game.
Normally alcohol isn't welcome at the game table (at least not drunk players) nor is stupid humor that would otherwise break immersion, but for this 1 4-part game a year everyone can go nuts and act like jack asses. And it is a ton of fun. Several years back when I ran the first I didn't expect it to catch on into being an annual tradition, but now it is looked forward to by all. Of course there are some limiations; the minors aren't allowed in these sessions at all, I do live in an apartment so being excessively loud or beligerant is out, and some other common sense rules for safety and consideration.
So does anyone else have an odd gaming tradition?
My old group has an annual new years game that's basically endurance D&D. Every December 31st we hold a throw-away game that begins in the early afternoon, usually by 3:00, and lasts until no one can stay awake any longer. We don't limit ourselves to D&D on these days - in fact, we often use this as a chance to try out a new gaming system. Our greatest session ever though was a good party vs. evil party setup. Each party had 6 PCs (large group) competing in the same dungeon, with a different GM running each group and frequently taking breaks so they could collaborate. At the end of the 16 hour session, the two parties met up on a giant chess board and did battle alongside golems that could only move in very specific ways.