When a story is primarily told and retold orally, it will change as a result of people misremembering details or adding their own attempts to improve it. Eventually there will be many variations of it in circulation, with none of them being considered official. The same has happened to the rules of some Tabletop Games.
Rulesets can vary wildly in both simple and complicated games. On the one hand, a simpler ruleset is more likely to have addendums to spice things up, but on the other, the more rules there are, the more likely one gets dropped or misremembered.
Most games that fall under this predate mass-market board games and involve common, simple components like a standard deck of cards. After all, almost all dedicated playing pieces show up in packages that also contain an official ruleset.
This also tends to happen for playground games (the problem of "games change when retold orally" is exacerbated when most players are kids) and Drinking Games (where the exact rules matter less than the fact that you get drunk from playing them).
Compare Popular Game Variant for when an official ruleset exists, even if people play a lot of different variants in practice. See also Calvinball for when the rules are literally made up as you go along.
Examples of real-life games:
- 22 has several house rules meant to either balance the game or make it more volatile. Here are some of the most common:
- Hand size: Instead of dealing at a constant hand size, the size of the next hand is equal to the score taken from the previous round.
- Skip the trades: The portion where cards are traded in is ignored - what you are dealt is what you get.
- Face cards: Instead of face cards having sequential score penalties, Jacks, Queens, and Kings all net a penalty of 10 points, while Aces only inflict 11. (Order still applies for trick-taking purposes)
- Optional heading: Heading the trick is optional. This means, just because a player is able to match or beat the highest card does not mean they have to.
- Straights: If a player has a run of cards in direct ascending value, this may be used to lead a hand. A minimum length, maximum length, or requirement to match suit may or may not be imposed.
- Reshuffling the point card: Traditionally, players hold onto their point card as a way to keep score. However, if paper and pencil (or equivalent) are on hand, this may be unnecessary, and the players may agree to shuffle them back into the deck.
- Dealer: If multiple people have the highest card on the last trick, the role of dealer is decided between them through random selection. Alternatively, the role of dealer simply passes counterclockwise throughout the game.
- Before the rules of Chess were properly formalized, different countries often had different rules. For instance, it was unclear whether pawn promotions were limited to place your captured pieces back on the board, or if they could promote into any non-king piece, the two-space initial pawn move and the en passant capture weren't immediately adopted everyone when they were first introduced, and there were various ways to handle the king's single-use special move which became castling in the formalized rules.
- Crazy Eights. The basic rules are a discard while following suit or value. This is the only thing that people can agree upon. The following are but a small example of the house rules one may come across.
- Eights: Usually wild. Sometimes, they change the suit to their own suit. Sometimes, the player gets to choose the suit they become. Other variants have it as skip a player.
- Twos: Pick up two. Stacking them usually means the next person picks up 4, then 6, then 8.
- Jacks: Skip a turn or reverse the rotation of players.
- Aces: "Drop the bomb." This allows you to play every other card of that suit on top of your ace.
- Queens: Pick up four. Stacking them might be additive, like with twos. Sometimes, you can add the twos to the run. Sometimes, only the Queen of Spades means picking up, and it usually means pick up 5. May or may not stack.
- Sixes: "Silent Six". Talking results in gaining two cards.
- King Of Hearts/Five Of Hearts: Dropping the King results in the next player taking five cards, unless they counter with the Five. If this happens, the player who used the King has to take ten cards.
- Multiples. Do you have -tuples of the same value? Why not play them all at once!
- Knock to declare your last card.
- And that doesn't even begin to cover Crazy Eights variants, like Crazy Eight Countdown.
- Hearts has no unified ruleset, though Omnibus Hearts codified several house rules, including the Queen of Spades as the 13-point penalty, the Jack of Diamonds as -10 points, Shoot the Moon, card passing, and opening with the 2 of clubs. The Microsoft game is basically Omnibus on the computer.
- Euchre: Originated in Germany with two Jokers (Jukers in German, pronounced like "yookers"), one Joker being high, the other low. These jokers could capture every other card played. The original deck size was 34 cards, Aces down to sevens, with the deuces and treys used as a point counting system. When brought to America (mostly the Midwest), the Jokers were omitted, with the Jack of trumps replacing the High Joker, and the Jack of same color as trumps replacing the Low Joker. The deck was also shortened to 24 cards, Aces down to nines, as two euchre decks could be made by splitting a pinochle deck. Thus, Euchre can be played with 2, 1 or 0 Jokers added to a deck of 32 or 24 cards.
- The basic idea of Kick the Can is that it works like Hide and Seek, but a captured player can be rescued if a still-free player kicks the can. There are a lot of variations
, such as changing how the can works, or even using multiple cans.
- Kings is a popular Drinking Game where the players draw a random card and have to perform the action associated with that card. There are so many rulesets about what the cards do that the game often starts by the players agreeing on just that.
- Early players of The Landlords Game personalized the game with their own rules and boards, often adjusting the properties to fit the region. The game was also known by other names, including Finance, Auction, Auction Monopoly and simply Monopoly. In the 1930's, Monopoly was patented and began to be mass-produced.
- Similar to Crazy Eights is Last Card. The usual rules are Ace is wild, 2 is pick up two, 5 is pick up five and 10 skip a turn. Optional rules include Jack is reverse, 7 'blocks' a 2 or 5, or bounces it back to person who put it down. Sometimes pick up cards can be passed on by the recipient by stacking another one on top to add the effect, regardless of whether it is the same number as the original pick up. There can be disagreements over whether someone's win was legitimate if they didn't call 'Last card' one turn, then emptied their hand next turn by putting down several cards of the same number.
- Liar's Dice: The base game involves bidding on the number of dice. Additional rules concern the value of Wild/Ace conversion bids (e.g. 1 any, 1 wild, 2 any vs 1 any, 2 any, 1 wild), Dice loss penalty (either 1 die or difference between bid and die), exact bids penalty, reveal and re-roll, calza (any player other then current challenge may declare spot-on), and palafico (special round for player with only one die left.)
- Mahjong: Variations generally relate to how hands are scored and when to call them. The base game allows calling mahjong once you have any recognized set, while some variations require a minimum score to make the claim.
- Solitaire card games often have subtle rules that get overlooked or misinterpreted, and it's likely made worse by the fact that the player has to be the arbiter of their own game when playing with real cards.
- Mao is similar to Crazy Eights or Uno, but different groups often have different starting rules (with more rules being added during the game). Fortunately, Mao is one of the few games where this actually works in the game's favor, since players are intentionally not told what the rules are — they have to deduce them through observation and trial and error.
- Oh Hell: Differences in the hand size sequence (e.g. Max > 1 > Max, or 1 > Max > 1), and variations on whether the dealer can bid in a way that allows the total number of tricks equal the current hand size.
- Pinochle: There's a few scoring systems circulating, such as Jacks and higher (value increases as card rank goes up), or kings and higher (where scoring cards are equally valuable). There are also variations on number of cards passed between the bidding team, and the cards used in the deck.
- President is a shedding game often used as a drinking game where you aim to get rid of your cards to become "president" in the next round. Wikipedia's page on it states that it's merely describing one variation of it, and there are many others.
- Spades: How Blinds (bidding X books before the cards are dealt) are supposed to work, or even if said gambit is available, is nebulous. Whether you can call for one at any time or only after you're down X points. Do you automatically get them if you go into negative points? Standard scoring for failed blind or double-points? Is the highest card the Ace of Spades, 2 of Spades, or a Joker? How these all work usually depends on who you play with.
- Spin the Bottle: Get all your friends in a circle, place a bottle on its side in the center of the circle, and go round-robin in spinning the bottle (a la Wheel of Fortune). In the game's most basic version, you must smooch on the lips whoever the bottle points to when it comes to rest. However, there are also a ton of variations with rules that determine who you can and cannot kiss (e.g. whether and which same-sex kisses are required, whether one has to kiss one's brother, sister, or other relation, etc., etc.), what the penalty is for not kissing a spun person, and other actions you can take.
- The tabletop RPG Traveller has two official rulesets at this time, the Traveller 5 system published by the game's creator, Marc Miller, and Mongoose Traveller, an officially licensed and supported edition published by Mongoose Publishing. Both are seen as official Traveller to all involved.
- While there are commercial versions of Werewolf (1997) (also known as Mafia), there's no definitive version of it. What roles are used, and exactly how they work, will usually vary.
Discussions and in-universe examples:
- Dario Fo's Corpse for Sale has the customer exploit the concept by asking to play Marseilles poker, but introduces the rules one a a time. First is "Cock-a-Doodle-Doo" being more valuable than winning hands, and the second is that said hand is only valuable if one player has it unique.
- Final Fantasy VIII has a card game Triple Triad, where each region has it's own ruleset concerning game variations (e.g. Open, Same, same Wall, Sudden Death, Random, Plus, Combo, Elemental) and card trading rules. Regions will have their rules change as the player visits different locations.
- Star Wars Legends: Much like poker, the card game sabacc has a lot of different regional variants. This becomes a significant plot point in the novel Dark Apprentice, when Lando Calrissian challenges Han Solo to a rematch of the game where Han won the Millennium Falcon: the two men play "random sabacc", where not only the card values but the entire set of house rules changes at random intervals, refereed in this case by C-3PO. Lando ends up winning by the skin of his teeth when the rules switch at the last second and give him a winning hand where he previously had a losing one.
