History ObviousRulePatch / CardGames

** One from the game's early days was the "Mewtwo Mulligan Deck" - a deck that simply had one copy of the original Mewtwo card and Psychic energy filling out the other 59 cards. Starting a hand without a Basic Pokemon (with only 1 Basic Pokemon in 60 cards, the probability of this is 53/60 = 88.3%) allowed the user to declare a mulligan, allowing them to draw another seven cards, and forced the other player to draw another card. This would keep going until the MMD user could either force a loss by running the other player out of draws before the game even began, or got their Mewtwo out and could use its power (to become immune to all damage) to stall the opponent out. A patch was put in to make the extra draw for the opposing player optional.

* One of the most blatant in cards rather than errata is "Writ of Accountability" from the ''Franchise/StarTrek Customizable Card Game'' (First Edition), which is essentially a list of {{Game Breaker}}s followed by "you lose". That is not an exaggeration. The consequence is literally an [[http://www.wixiban.com/images/ccg1e/roa/1EROA042.jpg automatic loss for anyone who's pursued one of a number of strategies.]] In tournament play, such a game (regardless of the situation prior to the Writ coming into play) grants 100 points to the winner, while the person who fell afoul of Writ scores 0. (Decipher generally tried to avoid outright ''banning'' cards. The ''only'' card on the STCCG ban list--"Raise the Stakes"--was on there because it violated gambling laws in the United States, not to mention that it would have wrought havoc with tournament play.)

*** Starting in the first ''Sword & Shield'' set, such Supporter cards of that effect are now called Professor's Research (which can feature a different Pokémon Professor depending on the set). Since a player can only have up to 4 copies of a specific named card in their deck, this limits the number of Pokémon Professor-related cards one can have in their deck.

** The trainer card Pokémon Catcher has the notoriety of being one of the only cards in the game to get nerfed. It allows you to switch your opponents active Pokémon with one of their benched Pokémon allowing the player to score easy kills on weak support Pokémon, on top of being able to be recycled by the trainer card Junk Arm. In the transition to the ''XY'' sets, Pokémon Catcher was errataed to require a coin flip to work. The trainer card Lysandre, released in the second ''XY'' expansion had the same effect with no coin flip, but it was a supporter card, meaning that using it meant locking yourself out of other supporters for the rest of the turn. Much like the "Professor's Research" example, later cards with the same effect would be named Boss's Orders (which can feature a different villain boss) and subject to similar restrictions.

* There are several rules in TabletopGame/{{Poker}} which are intended to promote speedy play and/or ban unethical maneuvers:
** Forced bets, including blinds, antes, and bring-ins, are designed to ensure that some or all players have a stake in the pot, preventing everyone from folding until they get a really good hand. In TournamentPlay, they are raised continually to prevent overly cautious play (this often leads to people winning World Championships with cards they wouldn't play in a low-limit cash game).
** The "small blind", "big blind", and "dealer button", used in cardrooms, particularly in Texas Hold'em, ensure that the action moves in an orderly manner, as opposed to previous opening rules like "forced bring-in" (the lowest (or sometimes highest) showing card has to open, common in stud games) or "jackpots" (common in draw games, requiring a hand of certain strength, often a pair of jacks, to begin the betting).
** "Cards Speak": A hand does not have to be declared at the showdown to be played (e.g., your flush still beats their three of a kind even if you don't know it's a flush when you show it down). This prevents ugly arguments about whether or not a player announced his best hand or should get credit for it.
** "Table Stakes": A player cannot be forced out of a pot due to lack of money (extra bets go into a side pot), and a player can't reach into their pocket and offer up their Aston Martin keys/the deed to the ranch/etc. to call a hand (the short player can only win the pots that their chips-in-play can "cover"). This prevents the richest person at the table from winning every hand by forced forfeit. Players are, however, allowed to add money to their reserve between hands.
** Anti-collusion rules such as: banning cellphones tableside, requiring cards shown to another player to be shown to the rest of the table, and banning languages other than English at the table. The last one often exempts [[UsefulNotes/SignedLanguage ASL]] from the ban, in order to avoid violating ADA requirements.
* One of the most obvious examples is {{Collectible Card Game}}s and their restricted/banned lists.

* At least by the ''Special Edition'' expansion pack, the ''TabletopGame/StarWarsCustomizableCardGame'' came with a separate glossary ''three times'' the size of the (already dense) basic rulebook, which was about 50% "errata" fixing {{Game Breaker}}s. The other half...well, let's just say this was a ''very involved'' game.
* In French ''Tarot'', a chelem is a bonus for winning every trick. The deck also contains a special card called excuse, which can never win a trick. Thus if a player has the excuse in his hand, he would normally not be able to complete a chelem. To patch this, if a player has already won all but the last trick and is left with only the excuse, it will win the trick regardless, completing the chelem. However, this is not enough: there is another bonus for taking the last trick with the smallest trump (number 1), so the player with both the excuse and the trump 1 would be unable to get that bonus while making a chelem. So in this case, winning the second to last trick with the trump 1 also awards the bonus.
* ''World Of Warcraft TCG''[='=]s rulebook should be called "exception book", really.
* One of the most blatant in cards rather than errata is "Writ of Accountability" from the ''Franchise/StarTrek Customizable Card Game'' (First Edition), which is essentially a list of {{Game Breaker}}s followed by "you lose". That is not an exaggeration. The consequence is literally an [[http://www.wixiban.com/images/ccg1e/roa/1EROA042.jpg automatic loss for anyone who's pursued one of a number of strategies.]] In tournament play, such a game (regardless of the situation prior to the Writ coming into play) grants 100 points to the winner, while the person who fell afoul of Writ scores 0. (Decipher generally tried to avoid outright ''banning'' cards. The ''only'' card on the STCCG ban list--"Raise the Stakes"--was on there because it violated gambling laws in the United States, not to mention that it would have wrought havoc with tournament play.)
** There exist a number of cards with that striped icon (called the "referee" icon) that exist almost exclusively to limit broken strategies (though some, like Defend Homeworld, have actual use beyond this). Writ is only the most punishing of these cards. Other cards result in lesser penalties. Some invoke a loss of points--going negative if they have to--or needing more points to win than usual. Others kill/destroy certain cards in play, or remove them from the game entirely (as in, they don't even go to the regular discard pile, they're simply placed out of play). Still others don't impose an actual penalty, but do impose limits on the use of certain cards.
** One nasty combination from the first set caused an actual rule change. The card "Telepathic Alien Kidnappers" allowed one player, once per turn, to name a card type (personnel, ship, interrupt, event, etc.), then pick a card from the opponent's hand. If it matched, the card was discarded. The card "Alien Probe" forced both players to play with their hands exposed, face-up on the table. The effect of the two cards together was that a player who had T.A.K. ''and'' Alien Probe could basically tell an opponent once per turn, "you lose ''that'' card". A later rules patch said that a player had to be allowed to conceal his hand before the opponent could try to pick a card with T.A.K., making the combo less deadly. In addition, other cards were introduced to counter both cards in the combo.
* The FAQ on the ''TabletopGame/{{Munchkin}}'' website is full of stuff like "No, thieves can not steal during combat or backstab themselves". This may be viewed as HypocriticalHumor since the term "Munchkin" refers to someone eking out every possible advantage they can from any game mechanic.
** They're willing to go along with a sufficiently devious rules abuse, though. One famous example is playing "Go Up A Level" cards on other players. Since some monsters will allow players to run away for free if they're below a certain base level, this could be used to force a player to fight that (often quite powerful) monster. The company's response:
--> ''This is [[NotTheIntendedUse not the original intent]] of "Go Up a Level" cards, but it is such a munchkinly and vile idea that [[ThrowItIn we like it too much to say no.]]''
** One card allowed you to change one die roll to be any number that you wanted it to be. However, they didn't specify that it had to be an integer ''between 1 and 6''. This led to people declaring that the die roll was one million or negative twelve or whatever, with bizarre results. They later changed the card so that you physically turned the die to display the number you wanted.
** Originally, the Wizard class could "charm" a monster by discarding their whole hand. Munchkin players being what they are, they immediately began "discarding their whole hands" when they had nothing in them. Later editions specify a minimum of three cards.

* In the trick-taking game ''[[http://boardgamegeek.com/boardgame/54307/chronicle Chronicle,]]'' wild cards have no suit and no value. There are six wild cards in the deck. Three of them are auto-win cards (the Demon beats everything but the King, the King beats everything, and the Dragon destroys the trick entirely) and three of them have effects unrelated to the trick (the Angel, Sage and Fool). So in theory, in a three-player game the players ''could'' play these three cards, resulting in the trick having no winner. The rules specify that the first player wins should this ever actually occur.
* The rules for Perfect Guard units in ''TabletopGame/CardfightVanguard'' have undergone a few pre-emptive changes:
** First, the wording for Perfect Guards was changed so that they could only protect one Unit at a time. One set later, Draconic Kaiser Vermillion was introduced, the first Unit with the ability to target three Units with one attack.
** Second, the "Sentinel" subtype was added to Perfect Guards, along with the condition that a deck could only have a maximum of four "Sentinel" cards. One set later, the first cards with ''two'' Clan types (Blaster Blade Spirit and Blaster Dark Spirit) were introduced[[labelnote:*]]This was significant because a Perfect Guard Unit can only protect a Unit from a matching Clan. Without this patch, the two Blaster Spirit cards could have had ''eight'' Perfect Guards to defend themselves with, something that could have been a GameBreaker[[/labelnote]].
* ''TabletopGame/IlluminatiNewWorldOrder'':
** The Limited Edition had a series of loopholes that would allow the Gnomes of Zurich to win on the first turn. The Unlimited Edition had a number of rule changes obviously designed to stop this exact scenario. Chiefly, the rule "Nobody may win on the first turn."
** The tournament rules allow organizers to invalidate trades in multiplayer tournaments that are solely designed to throw the game to one player and advance them to a higher table (or victory in the tournament). They admit that such a tactic is highly Illuminated, but it really isn't fair to the outsider who gets screwed over by team-players.
* In the ''TableTopGame/MyLittlePonyCollectibleCardGame'', there are three cards named "Applebloom, Showstopper", "Scootaloo, Showstopper", and "Sweetie Belle, Showstopper", that have effects that make the player either tell a joke, sing, or dance, respectively. These were later made to be optional, as they were written "in the spirit of fun".

* TabletopGame/{{Bridge}} has one from the days of its foundation - eight-level contract bids. A contract obligates the declaring team to take six tricks (the "book tricks") on top of the number (the "bid tricks") of the contract. As there are only 13 tricks to play, the highest contract that can be made is a seven-level contract. However, depending on distribution, it's quite possible that the penalty for making a sacrifice bid at the eight-level would be lower than the reward for making the grand slam at the seven-level, making it more profitable to make the sacrifice, even with the guaranteed penalty double. This was seen as unsporting (and a bit dull on many occasions), so the rules were amended to make it impossible to promise to take more tricks than a hand can hold.
* The ''Final Fantasy Trading Card Game'' had a rule patch in response to the evolution of the game. Lani was introduced in the Opus XII expansion. When she enters the field, the opposing player removes the top card of their deck from the game, and the player who played Lani can then cast the card as if it was in their hand and at a reduced cost. This caused confusion, as "cast" was at the time defined as "playing a Summon", which are one-time effects. Forwards, Backups, and Monsters until then were never "cast", but "played". Creator/SquareEnix quickly clarified that the word "cast" was being redefined to "paying a cost in Crystal Points to play a card from your hand" and that all cards paid for and played that way were "cast", regardless of their card type. "Play" in turn was redefined as "putting a card onto the field, whether it had a cost paid for or not". The distinction is important, as several cards have special effects depending on how many cards you "cast" as opposed to "played".
* ''TabletopGame/TwentyTwo'':
** If, for whatever reason, there aren’t enough cards in the deck to give all players a complete hand (either a lot of players, or landing a high card with the appropriate house rule), the dealer stops when cards cannot be dealt evenly, leaving the remainder as a trading pool.
** While not all groups allow for straights, among those that do, it’s common to require three or more cards so players can’t simply offload two adjacent cards.

* ''TabletopGame/YuGiOh'':
** Lists in game started as just the Limited List: normally, you can have up to three of any one card in a deck, but for game balance reasons the Limited List mandates that only one (Limited) or two (Semi-Limited) copies of certain cards can be included in a deck. Before long, players were discovering interesting ways to break the game using card combos the game designers hadn't foreseen, resulting in absurdly powerful decks that could force a win in a single turn (or even the first turn). Thus the Limited List was expanded to include Forbidden Cards, which cannot be included in a deck at all. The list is changed roughly every six months, with cards being both added to and sometimes removed from it.
** In an interesting take on this, the formerly-Limited card "Twin-Headed Behemoth" was taken off the list because of a ruling change: Its effect (which lets it revive itself from the Graveyard at the end of the turn it's destroyed from the field with 1000 ATK and DEF) specifically states it can only be activated "once per duel". It was put at 1 after it was pointed out that multiple copies of the card would make it impossible to keep track of which copy had used its effect and which haven't, meaning anyone could abuse the confusion and reuse the card's effect illegally. Now, though, the card's ruling has changed so that only 1 copy of it owned by a player can activate its effect per duel, period. The rule change was completely arbitrary, only allowing the card to become unlimited without interfering with the reasons it was limited in the first place. A similar case happened with Treeborn Frog, which won't activate if one is already on the field, allowing it to be unlimited.
** The worst examples of this in Yu-Gi-Oh are Yata-Garasu and the two Envoys. All of the other cards on the Forbidden list are pivotal in combos. These three cards were banned just because they were ''[[GameBreaker that broken.]]'' Not helping the Envoys' case is a rule known as priority, which allows the player to activate their effects (which can normally only be activated at times when the player could activate a Normal Spell) immediately when they're Summoned, before the opponent has the chance to activate cards that would destroy them. Following the introduction of the Xyz monsters in the game, the OCG and TCG had their priority rulings patched to prevent people from calling priority on Ignition monster effects. Black Luster Soldier - Envoy of the Beginning has since been taken off the list. Chaos Emperor Dragon required errata to undo its banning: the player cannot activate any other card effects on the turn its nuke is used, and the damage is only done with respect to the opponent's cards that are sent to the Graveyard. Of the three cards, only Yata remained banned for a long time (The latest banlist made it Limited). [[note]]Yata-Garasu was a 200 ATK spirit monster that made the opponent skip their next draw phase whenever it connected. Because it bounced itself at the end of turn, it was effectively immune everything other than Quick-Play and Trap cards, so if it got through, and you didn't have an answer that very second, you almost certainly lost the game. and you have to sit there and take 200 damage each turn and hope he milled out before he killed you. [[/note]]
** Green Baboon, Defender of the Forest, is another monster with an unusual story: its effect allows the controller to pay 1000 LP to summon it from your hand or Graveyard if a Beast-Type monster you control is destroyed, but too many duelists were exploiting that effect by bringing it out by purposely suiciding their Beasts in battle. As such, Konami arbitrarily decided its effect can't go off if the Beast monster was destroyed by battle. This significantly weakened the monster's power and caused many players to declare TheyChangedItNowItSucks, but there's a twist to the tale. Shortly after the ruling was implemented, guess what came out? A new monster, with the ''exact same stats'' as the original Baboon (and even named ''Yellow'' Baboon, ''Archer'' of the Forest), and the ability to summon itself from the hand if a Beast you control is destroyed by battle (this time requiring the controller to [[DeaderThanDead banish]] two Beast-Type monsters from their Graveyard to do so, instead of paying LP).
** Also, the "Archfiend" cards, an issue resulting from {{bowdleriz|e}}ation of card names. In the Japanese version, several cards used the word "Demon" in their names, and this word was changed into a bunch of different words in the initial American releases: "Demon's Summon" became "Summoned Skull", "Demon's Axe" became "Axe of Despair", and so on. This worked fine until a series of cards that specifically dealt with cards with "Demon" in their names started to come out, so a ruling had to be issued to declare "Archfiend" as a "special category of card" which included all the cards that had "Demon" in the Japanese name. From then on, "Demon" would always be translated as "Archfiend". Later on, new printings of the Archfiend cards would include rules text stating that they were treated as Archfiends at all times, even on the Normal Monsters.
** In general, the TCG is prone to having cards be renamed in later releases, when they are incorporated into later-released archetypes and there's no easy way for the English card text to cover them. Other than the Archfiends, probably the most prominent example of this is the capitalization of "HERO" in groups of cards such as the "Elemental HERO" and "Destiny HERO" series, due to the introduction of new sub-archetypes of [=HEROes=] that weren't foreseen by the creators (and the existence of other cards, not connected to these archetypes, with "Hero" in the name).
** The [[http://yugioh.wikia.com/wiki/Guardian "Guardian"]] Archetype was another nightmare when it was first introduced. This caused the [[http://yugioh.wikia.com/wiki/Arsenal_Summoner one card]] that specifically designates a "Guardian" card to include a long list of cards that it does not apply to because they do not have "Guardian" in their names in Japanese.
** Cards have been retroactively given new names because of an archetype released years after it was first introduced, or because their current name conflicted with a new Archetype that they didn't belong in. A prime example is [[http://yugioh.wikia.com/wiki/Sky_Scout Sky Scout,]] formerly known as "Harpie's Brother". It was never intended to be a Harpie monster (its Japanese name is "Birdman"), but at the time it didn't matter too much since all the cards that worked with Harpies specifically only worked with "Harpie Lady". Later, more Harpie cards came out with a wider range of support, so to save card space from having to specify that "Harpie's Brother" didn't count, the card was renamed.
** With the release of Xyz Monsters, there was a brief period where there were very few written rules about how they actually work - one key problem was the fact that the monster used for Xyz Summoning stayed on the field until "detached" by an effect. Fine, but when do effects that specify when a monster "leaves the field" trigger? WordOfGod said that they trigger on Xyz Materials being detached, and ''all hell broke loose''. Two already powerful cards got so absurdly broken that a single copy could easily fetch well over 100 dollars. Konami quickly made a rule change: Xyz Materials being detached ''never'' trigger such effects, because they aren't treated as cards anymore. It's just as weird as it sounds.
*** These two cards were "Sangan" and "Tour Guide from the Underworld", along with any given Rank 3 (at the time, Number 17 Leviathan Dragon was favored). The combo is this: Tour Guide is summoned, whose effect summons a level 3 Fiend-type monster from the Deck, at the cost of negating that monster's effect. This monster would be Sangan. They overlay to form Number 17, whose effect is to "detach" a card to become stronger. The effect negation of Tour Guide is now void, since Sangan's state has changed. Number 17 detaches Sangan to become stronger, and Sangan's effect activates: when it is sent from the field to the graveyard, it adds a 1500-ATK-or-less monster from the Deck to the hand, such as another Tour Guide. So, to summarise, at no loss of hand advantage (a very important resource in Yu-Gi-Oh), you have a 2500 ATK beatstick facing your opponent down. This is no longer possible due to the new ruling. That said, cards that activate when "sent to the graveyard" will still activate - just not the ones that require being sent from the field to the graveyard.
** "Light and Darkness Dragon" has so much text on it that Upper Deck/Konami never fit a very important sentence on it: its negation effect can only activate once per chain. If Konami had never announced that ruling, Light and Darkness Dragon would continually keep activating to negate ITSELF until its attack and defense got so low that it couldn't activate any more. This ruling also gives Light and Darkness Dragon its main weakness, which is that a card can be chained to its effect, which it will be unable to negate.
** In early 2015, a card-specific rule patch was introduced: "Dark Strike Fighter", a card banned mere months following release given its ease of summoning, high attack, and powerful burn effect, had the latter effect limited to Main Phase 1, and only once per turn, period. Sadly though, with the attack and burn for OTK shenanigans largely curbed, most fans decried it as a JokeCharacter whose role as a reliable level 7 Synchro was completely outclassed to the point that it became Unlimited after its errata and has been forgotten from the metagame ever since.
** On occasion, Konami/Shueisha have been known to create less overpowered counterparts or cards performing similar functions as replacements for cards retired to the Forbidden list either before or after the fact - Tradetoad for Substitoad, Rescue Rabbit for Rescue Cat, Fishborg Launcher for Fishborg Blaster, Demise, King of Armageddon, Ruin, Queen of Oblivion, and Sky Scourges Enrise and Norleras for the Envoys, being notable examples.
** As of the 2015 change to Dark Strike Fighter, Konami has taken an interesting stance. Now, every so often they introduce [[http://yugioh.wikia.com/wiki/Errata errata]] by changing card text to one or multiple cards on the Forbidden List. While before they were just rule patches, as of Dark Strike Fighter and beyond they're doing it simply to curb the power of certain cards. Notable examples are Crush Card Virus and Ring of Destruction. The overriding sentiment is, it's better to make a card weaker and actually usable than keep them as strong as they are originally and have them remain on the list forever.
** Several cards that were released starting from [=ZeXal=] era have been given an "only once per turn" rule because many pro players abused infinite loops and lack of once per turn restrictions to form easy one-turn or even first-turn kills. In fact, one player even managed to win a world championship by using a Frog FTK deck, leading it to be completely neutered by the following banlist.
** Following Link-climbing shenanigans involving Crystron Needlefiber, Isolde, Two Tales of the Noble Knights, and Summon Sorceress, several Link Monsters capable of field swarming introduced in later sets are unable to be used as Link Material the turn they are Link Summoned, specifically require an in-archetype monster to be used as Link Material or restricts on what monsters that can be special summoned. Additionally, starting from SEVENS era, many of the introduced archetypes that does not revolve around Link Summoning severely restricts the player from special summoning or activating effects outside of their designated archetypes.
** After cards that easily Special Summoned multiple Token monsters like Dandylion or Grinder Golem got themselves on the banlist for providing easy Link Material for Link climbing shenanigans, subsequent Link Monsters would specify their (otherwise generic) Link Material requirements as either non-Token monsters, monsters with different names, or both. Subsequent cards that churns out easy Tokens now either prevents them from being used as Link Materials or restricts the player from Link Summoning for the rest of the turn.
** A German player, Maik S., [[https://www.youtube.com/watch?v=Ns17sYK4Eag entered the 2007 German National Tournament with a 2,222-card Main Deck and 222 card Fusion Deck]], as part of a joke with a friend. Maik, himself an official judge for Upper Deck Entertainment (the company running the tournaments), knew there was only a minimum deck size limit for the main deck or the Extra Deck (then known as the Fusion Deck), without a maximum. The deck used was practically impossible to shuffle effectively, could not have easily verified contents, and [[https://yomifrog.lima-city.de/2222_card_deck_ygo/index.php?lang=en used a specially constructed hand that could be seen from several tables away.]] After the first duel, the event's chief judges convinced Maik to drop out of the tournament. In less than 1 year, the first ever standardized "Master Rules" format introduced a restriction on deck sizes to 60 cards, and a restriction on Fusion (Extra) Deck size to 15 cards, limitations that have stayed in place to this day. This occurence at a national event may have led to this rule being put in place.
*** The deck, which was practically impossible to use effectively, included effects that would require the deck to be shuffled afterward. As this would take a very long time to be shuffled, judges ruled him out of the tournament as it could cause games to take a very long time and thereby hold up the entire tournament. It was also highly inconvenient for judges, because in the event that they needed to do a deck check (which would require them to inspect each card in the deck and compare it against the deck list the player provided, which in this case was several pages long), it would, again, take a very long time.
*** Maik would go on to be an even more influential judge, authoring some of the clarifications and rulings that addressed key holes in the game. Some of these rules are used to this day.
** In ''VideoGame/YuGiOhMasterDuel'', one of the first event hosted in the game was an [=Xyz=] festival that forced players to use only [=Xyz=] monsters, banning not just non-Xyz Extra deck monsters but also archetypes that don't revolve around Extra deck plays such as Eldlich and Monarchs to prevent players from cheesing the event. To encourage players to participate in the event, players are awarded Gems even if they lost the duel (100 for winning & 50 for losing and none at all if they surrender). However, players soon found out that it was far more efficient to lose twice in quick succession than to play a legitimate game that could last up to 15 minutes, thus this caused most of them to run self-burn decks that was designed to quickly deplete their own LP as fast as possible in order to attain gems as efficiently as possible, with only little investment required compared to the cost of building a competent [=Xyz=] deck. As a result, Konami increased the reward for winning from 100 to 500 in order to incentivize legitimate [=Xyz=] duels. Subsequent events such as [=N/R=] and Synchro Festivals flat-out bans any cards that purposely deplete your LP as fast as possible while still keeping the greater reward for winning in order to deter any further self-burn decks in the events.

* There are times ''TabletopGame/MagicTheGathering'' has had to give cards errata. It is currently not their policy to reword a card for simply being too powerful, but there are quite a few cards that have different wordings due to rules changes, or interactions that literally break the game (as in, "create situations that the rules don't cover"). This was exacerbated with two major rules changes ('96 and '09).
** The old errata policy allowed cards to be errata'd for power reasons, but this has since been reverted. Overpowered cards are now banned. For example, [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=642 Time Vault]] has been errata'd multiple times with various awkward wording to ensure there was ''no way'' to easily untap it and gain infinite [[ExtraTurn extra turns.]] The current rules text, while much simpler than even the original card, makes the card obviously broken in half (and banned almost everywhere). However, a few cards have errata intended to make them function as they would have under the rules at the time, such as [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=5193 Mox Diamond]] and [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=4593 Lotus Vale]] not allowing you to "cheat" past their requirements (as would have been true at time of release).
** [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=159249 Animate Dead]] has generally worked as it was originally intended: it enchants a creature and [[AnimateDead brings it back from the dead,]] but the creature dies if the enchantment goes away, just like the various Necromancy spells from ''TabletopGame/DungeonsAndDragons''. However, the exact mechanics of this process, if and how a creature that would be immune to Black spells can be targeted by this, etc., have caused Animate Dead to be a nightmare of errata and Magic legalese. There's a reason only two other cards like Animate Dead have ever been made, and every other reanimation spell thereafter is an instant or a sorcery.
** The Sixth Edition rules changes were done, in part, to deal with all the Obvious Rule Patches that were made to the game over time, such as how Wizards of the Coast dealt with [[http://gatherer.wizards.com/pages/card/Details.aspx?multiverseid=30 Mana Vault.]] The card's text states that it taps for 3 colorless mana, doesn't untap unless you pay 4 mana, and deals 1 damage to you each turn it stays tapped. The problem is that the game rules stated that a tapped artifact didn't function, so the abilities that keep it tapped, let you pay 4 to untap it, and make you take 1 damage if you don't untap it shouldn't work. The solution was a patch that allowed Mana Vault to work as written. After Sixth Editon, they simply removed the rule about tapped artifacts not working, since it really only mattered in a few situations anyways.
** Before [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=383131 Time Walk]] was released, it was phrased "Target opponent loses next turn", which itself needed to be rewritten after people started misinterpreting it as "Target opponent ''loses the game'' next turn". (It's still massively overpowered though.)
** The standard Constructed Deck construction rules of today are a pretty important rules patch. Originally, there simply were no deck construction rules ([[https://magic.wizards.com/en/articles/archive/original-magic-rulebook-2004-12-25 Alpha rules for reference]]). Revised Edition added a minimum of [[https://mtg.gamepedia.com/Revised_Edition/Rules_changes 40 cards in a deck.]] By Fourth Edition, the modern rules played by today came about -- at least 60 cards, and no more than 4 copies of any non-basic-land card. Had there remained no restrictions, theoretically a player could create decks that could win on the first turn nearly 100% of the time (assuming somebody willing to hunt down the requisite number of rare cards to make them work).
** Speaking of [[TabletopGame/MagicTheGathering Magic,]] a few powerful creatures ([[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=5713 Serra Avatar,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=191312 Darksteel Colossus,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=140214 Purity,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=140168 Dread,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=189213 Guile,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=140227 Vigor,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=189214 Hostility,]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=179496 Progenitus,]] and ''[[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=193632 Kozilek, Butcher of Truth]]'') have an ability that prevents them from going to the graveyard, shuffling them back into the deck instead. While this looks like an advantage, it was done to prevent players from discarding these powerful creature cards on purpose so that they can revive them using ''way'' cheaper AnimateDead spells. This is not an idle concern, as entire decks are built around this very tactic.
*** Note that only the Colossus and Progenitus actually avoid hitting the graveyard. The other 6 simply don't stay there for very long, meaning that aforementioned shenanigans are still possible, albeit a bit more difficult.
*** Similarly, some creatures have abilities that only trigger "when you cast [the creature]" (which means to play it from your hand manually by paying its mana cost) to prevent reanimation shenanigans.
*** Taking this even further, the card [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=106427 Phage the Untouchable]] has an ability that causes you to ''lose the game'' if you didn't cast her from your hand. Like the above examples, this is done to prevent "reanimation" exploits. (It should be noted that Phage's ''other'' ability is to cause the ''opponent'' to lose the game if she manages to lay a finger on him, so ensuring the "Impractical" part of AwesomeButImpractical was kind of necessary in her case.)
** At one point, the Comprehensive Rules contained a line which read [[ThereIsNoRuleSix "Ignore ]][[LogicBomb this rule".]] This was because the rule no longer existed but Wizards didn't want to change the numbering to close the gap (as it would screw up all references to rule numbers).
** The introduction of a "Planeswalker" card type almost fifteen years after the game's inception necessitated such a patch. Planeswalkers needed to be valid targets for damage, but since they hadn't existed previously, all existing damage spells only targeted creatures and/or players, of which planeswalkers were neither. So a special patch rule was added that allowed spells to redirect their damage from a player to their planeswalker. The rules tolerated this ugly workaround for nearly a decade before a [[http://markrosewater.tumblr.com/post/166162774138/what-planeswalker-redirection-rule-change sweeping errata]] was made to change every previous instance of "damage target player" to "damage target player or planeswalker".
** The "M10" major rules overhaul included changes to the combat rules, which would have made the Deathtouch ability almost entirely useless, so, in the M10 rules, Deathtouch got a special rule exempting it from the new combat rules. It has since been further patched to work properly under the new rules.
** The card [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=46724 Mindslaver]] lets you control a player's turn. Despite multiple rulings from the beginning that say "no, you can't make your opponent concede the game with this", there will always be somebody who tries to get away with this. An interesting corollary is if Mindslavering someone (perhaps endlessly) can ''stop'' them from conceding by denying them ever getting a turn, but no, there is a special rule ([[http://media.wizards.com/2017/downloads/MagicCompRules%2020170925.txt 104.3a]]) that says concession is a special action that can be taken at any time by a player and is completely unstoppable by anything else.
*** It's irrelevant now, but the other Obvious Rule Patch with Mindslaver at the time of release was to just arbitrarily say that when another player controls your turn, you don't suffer "mana burn". Otherwise the correct thing to do would be to simply tap all lands and deal a ton of damage to yourself, which is less cool than using your own cards against you and making terrible decisions. Not needed anymore after the mana burn rule itself was abolished for almost never doing anything.
** When [[http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Stoneforge%20Mystic Stoneforge Mystic]] got banned, [[http://archive.wizards.com/Magic/magazine/article.aspx?x=mtg%2fdaily%2ffeature%2f148 the announcement]] came a mere 10 days after the release of an event deck containing two copies of it. Wizards of the Coast added a stipulation to the ban that that deck was legal even with the two Stoneforge Mystics, provided that it had not been modified in any way.
** The original rules for spell resolution order were such a [[http://archive.wizards.com/Magic/Magazine/Article.aspx?x=mtgcom/arcana/130 maze]] of patches Sixth Edition decided to replace it with an entirely new system.
** Want to give a would-be rules expert a headache? Ask about [[LogicBomb the interaction between]] [[http://gatherer.wizards.com/Pages/Card/Details.aspx?name=HUMILITY Humility]] and [[http://gatherer.wizards.com/Pages/Card/Details.aspx?name=opalescence Opalescence]].
** The ''Shadows over Innistrad'' set introduced a double-faced card, [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=409831 Startled Awake]], that's a sorcery on one side and a creature on the other. (It can be put onto the battlefield transformed as a creature from a graveyard.) The problem is: What if some effect now transforms it? It would be a sorcery card on the battlefield, which is nonsensical. A previously existing rule states that a sorcery cannot enter the battlefield, but that doesn't cover this case, because transforming is not entering the battlefield. Instead, a rule was added that if there's a sorcery (or instant) on the other side of the card, and an effect tries to transform it, it simply doesn't transform.
** Wizards' policy of not errata'ing for balance reasons came to a head with the introduction of the 'Companion' mechanic in ''Ikoria: Lair of Behemoths.'' A Companion card could be placed in your sideboard and played from there for their normal mana cost, any time you wanted, provided your deck adhered to certain deckbuilding restrictions such as "every permanent card in your deck has converted mana cost 2 or less." The cards were looked at with skepticism before release, only for that skepticism to turn to horror very quickly when it was realized that these cards were extremely strong. Their effects were certainly powerful, but the fact that the core mechanic allowed you to essentially start with a free card that you could play any time was so invaluable that many of them saw heavy play in a variety of formats. Two of them, [[https://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=479746 Lurrus of the Dream Den]] and [[https://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=479753 Zirda, the Dawnwaker]], were very quickly banned in Legacy and Vintage as their requirements were extremely light for those formats, and bans for Standard were expected to come. Faced with the very real prospect of having to ban a significant number of them in many formats, Wizards made the unprecedented decision to nerf the entire mechanic via an errata, changing it to simply allowing you to draw the card into your hand for 3 mana rather than play it for its cost. Even still at least one Companion ([[https://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=479752 Yorian, Sky Nomad]]) still sees play in Standard.
*** [[https://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=479747 Lutri, the Spellchaser]] was preemptively banned from Brawl on release, because the format rules rendered the companion restriction moot, meaning any deck using red and blue could run it with effectively no drawback at all.
** There used to be rather game-breaking combinations of cards owing to a quirk in the rules regarding life. Upon the initial release of ''Magic'', a player would only lose the game if they had zero life at the end of their turn. This allowed players to spend more life than they had to cast super-powerful spells, then crafting some sort of other card combo to bring their life back above zero before their turn ended. The rules were eventually changed so that a player loses instantly when their life hits zero, shelving these card combos.
** Meant to deal with trolling attempts similar to the Yu-Gi-Oh! case above (and possibly inspired by him in particular), ''Magic'' requires that the player be able to shuffle their deck, using only their hands, in a reasonable timeframe (as decided by the judge, who may also get a proxy for the player if they're disabled). It's 250 cards in the online version ''Arena'', which has no physical limits because the computer handles the shuffling; however, doing it online means it's harder to troll the other player, and a 250-card deck is going to be ''incredibly'' bad.

** The worst examples of this in Yu-Gi-Oh are Yata-Garasu and the two Envoys. All of the other cards on the Forbidden list are pivotal in combos. These three cards were banned just because they were ''[[GameBreaker that broken.]]'' Not helping the Envoys' case is a rule known as priority, which allows the player to activate their effects (which can normally only be activated at times when the player could activate a Normal Spell) immediately when they're Summoned, before the opponent has the chance to activate cards that would destroy them. Following the introduction of the Xyz monsters in the game, the OCG and TCG had their priority rulings patched to prevent people from calling priority on Ignition monster effects. Black Luster Soldier - Envoy of the Beginning has since been taken off the list. Chaos Emperor Dragon required errata to undo its banning: the player cannot activate any other card effects on the turn its nuke is used, and the damage is only done with respect to the opponent's cards that are sent to the Graveyard. Of the three cards, only Yata remains banned. [[note]]Yata-Garasu was a 200 ATK spirit monster that made the opponent skip their next draw phase whenever it connected. Because it bounced itself at the end of turn, it was effectively immune everything other than Quick-Play and Trap cards, so if it got through, and you didn't have an answer that very second, you almost certainly lost the game. and you have to sit there and take 200 damage each turn and hope he milled out before he killed you. [[/note]]

** If something is shown to be a GameBreaker, the most common means of addressing this is to release a new card a few sets later that serves as a hard counter to said GameBreaker. The most notable instance is the rise of Pokémon-SP, strong Basic Pokémon released alongside supplementary cards that allowed them to be directly searched out from a deck, shuffled around the table, gain additional attack effects, and so forth. This proved to dominate tournament play. The response was to release [[http://bulbapedia.bulbagarden.net/wiki/Machamp_(Stormfront_20) Machamp]] in the Stormfront set [[note]]Which actually came out ''before'' the set which introduced Pokémon-SP[[/note]], which has a low-cost attack that, if used on a Basic Pokémon, knocks it out.

** In ''VideoGame/YuGiOhMasterDuel'', one of the first event hosted in the game was an [=Xyz=] festival that forced players to use only [=Xyz=] monsters, banning not just non-Xyz Extra deck monsters but also archetypes that don't revolve around Extra deck plays such as Eldlich and Monarchs to prevent players from cheesing the event. To encourage players to participate in the event, players are awarded Gems even if they lost the duel (100 for winning & 50 for losing and none at all if they surrender). However, players soon found out that it was far more efficient to lose twice in quick succession than to play a legitimate game that could last up to 15 minutes, thus this caused most of them to run self-burn decks that was designed to quickly deplete their own LP as fast as possible in order to attain gems as efficiently as possible, with only little investment required compared to the cost of building a competent [=Xyz=] deck. As a result, Konami increased the reward for winning from 100 to 500 in order to incentivize legitimate [=Xyz=] duels. Come the [=N/R=] festival, any cards that can purposely deplete your LP as fast as possible have been banned from the event.

** In ''VideoGame/YuGiOhMasterDuel'', one of the first event hosted in the game was an [=Xyz=] festival that forced players to use only [=Xyz=] monsters, banning not just non-Xyz Extra deck monsters but also archetypes that don't revolve around Extra deck plays such as Eldlich and Monarchs to prevent players from cheesing the event. To encourage players to participate in the event, players are awarded Gems even if they lost the duel (100 for winning & 50 for losing and none at all if they surrender). However, players soon found out that it was far more efficient to lose twice in quick succession than to play a legitimate game, thus this caused most of them to run self-burn decks that was designed to quickly deplete their own LP as fast as possible in order to attain gems as efficiently as possible, with only little investment required compared to the cost of building a competent [=Xyz=] deck. As a result, Konami increased the reward for winning from 100 to 500 in order to incentivize legitimate [=Xyz=] duels. Come the [=N/R=] festival, any cards that can purposely deplete your LP as fast as possible have been banned from the event.

** In ''VideoGame/YuGiOhMasterDuel'', one of the first event hosted in the game was an [=Xyz=] festival that forced players to use only [=Xyz=] monsters, banning not just non-Xyz Extra deck monsters but also archetypes that don't revolve around Extra deck plays such as Eldlich and Monarchs to prevent players from cheesing the event. To encourage players to participate in the event, players are awarded Gems even if they lost the duel (100 for winning & 50 for losing and none at all if they surrender). However, players soon found out that it was far more efficient to lose twice in quick succession than to play a legitimate game, thus this caused most of them to run self-burn decks that was designed to quickly deplete their own LP as fast as possible in order to attain gems as efficiently as possible, with only little investment required compared to the cost of building a competent [=Xyz=] deck. As a result, Konami increased the reward for winning from 100 to 500 in order to incentivize legitimate [=Xyz=] duels.

** In ''VideoGame/YuGiOhMasterDuel'', the one of event hosted was an [=Xyz=] festival that forced players to use only [=Xyz=] monsters, banning not just non-Xyz Extra deck monsters but also archetypes that don't revolve around Extra deck plays such as Eldlich and Monarchs to prevent players from cheesing the event. To encourage players to participate in the event, players are awarded Gems even if they lost the duel (100 for winning & 50 for losing and none at all if they surrender). However, players soon found out that it was far more efficient to lose twice in quick succession than to play a legitimate game, thus this caused most of them to run self-burn decks that was designed to quickly deplete their own LP as fast as possible in order to attain gems as efficiently as possible, with only little investment required compared to the cost of building a competent [=Xyz=] deck. As a result, Konami increased the reward for winning from 100 to 500 in order to incentivize legitimate [=Xyz=] duels.

* Lists in the ''TabletopGame/YuGiOh'' card game started as just the Limited List: normally, you can have up to three of any one card in a deck, but for game balance reasons the Limited List mandates that only one (Limited) or two (Semi-Limited) copies of certain cards can be included in a deck. Before long, players were discovering interesting ways to break the game using card combos the game designers hadn't foreseen, resulting in absurdly powerful decks that could force a win in a single turn (or even the first turn). Thus the Limited List was expanded to include Forbidden Cards, which cannot be included in a deck at all. The list is changed roughly every six months, with cards being both added to and sometimes removed from it.

*** In general, the TCG is prone to having cards be renamed in later releases, when they are incorporated into later-released archetypes and there's no easy way for the English card text to cover them. Other than the Archfiends, probably the most prominent example of this is the capitalization of "HERO" in groups of cards such as the "Elemental HERO" and "Destiny HERO" series, due to the introduction of new sub-archetypes of [=HEROes=] that weren't foreseen by the creators (and the existence of other cards, not connected to these archetypes, with "Hero" in the name).
*** The [[http://yugioh.wikia.com/wiki/Guardian "Guardian"]] Archetype was another nightmare when it was first introduced. This caused the [[http://yugioh.wikia.com/wiki/Arsenal_Summoner one card]] that specifically designates a "Guardian" card to include a long list of cards that it does not apply to because they do not have "Guardian" in their names in Japanese.
*** Cards have been retroactively given new names because of an archetype released years after it was first introduced, or because their current name conflicted with a new Archetype that they didn't belong in. A prime example is [[http://yugioh.wikia.com/wiki/Sky_Scout Sky Scout,]] formerly known as "Harpie's Brother". It was never intended to be a Harpie monster (its Japanese name is "Birdman"), but at the time it didn't matter too much since all the cards that worked with Harpies specifically only worked with "Harpie Lady". Later, more Harpie cards came out with a wider range of support, so to save card space from having to specify that "Harpie's Brother" didn't count, the card was renamed.

*** These two cards were "Sangan" and "Tour Guide from the Underworld", along with any given Rank 3 (at the time, Number 17 Leviathan Dragon was favored). The combo is this: Tour Guide is summoned, whose effect summons a level 3 Fiend-type monster from the Deck, at the cost of negating that monster's effect. This monster would be Sangan. They overlay to form Number 17, whose effect is to "detach" a card to become stronger. The effect negation of Tour Guide is now void, since Sangan's state has changed. Number 17 detaches Sangan to become stronger, and Sangan's effect activates: when it is sent from the field to the graveyard, it adds a 1500-ATK-or-less monster from the Deck to the hand, such as another Tour Guide. So, to summarise, at no loss of hand advantage (a very important resource in Yu-Gi-Oh), you have a 2500 ATK beatstick facing your opponent down. This is no longer possible due to the new ruling.
*** That said, cards that activate when "sent to the graveyard" will still activate - just not the ones that require being sent from the field to the graveyard.

* The ''Final Fantasy Trading Card Game'' had a rule patch in response to the evolution of the game. Lani was introduced in the Opus XII expansion. When she enters the field, the opposing player removes the top card of their deck from the game, and the player who played Lani can then cast the card as if it was in their hand and at a reduced cost. This caused confusion, as "cast" was at the time defined as "playing a Summon", which are one-time effects. Forwards, Backups, and Monsters until then were never "cast", but "played". Creator/SquareEnix quickly clarified that the word "cast" was being redefined to "paying a cost in Crystal Points to play a card" and that all cards paid for and played were "cast". "Play" in turn was redefined as putting a card onto the field, whether it had a cost paid for or not. The distinction is important, as several cards have special effects depending on how many cards you "cast" as opposed to "played".

** In the ''Black & White'' sets, there was "Professor Juniper" a Supporter card that allows you to discard your hand and draw 7 cards, which was reprinted towards the end of that generation. The first ''XY'' set gave us "Professor Sycamore", a Supporter card with the ''exact same effect'', which meant you could have 8 copies of basically the same card in your deck. Being aware of this, Nintendo issued a rule stating you aren't allowed to run Professor Juniper and Professor Sycamore at the same time (this ruling would include the "Professor's Research" card mentioned below).

* In the early days of the ''TabletopGame/{{Pokemon}} Trading Card Game'', there was a loophole where a deck that contains no Basic Pokémon would prevent the game from ever starting. This is because each player must play down a Basic Pokémon in order to start the game. Thus, when Nintendo bought the card game back from Wizards of the Coast (who wasn't taking it seriously to begin with), Nintendo created a rule for all competitions, regardless of purpose: All decks must contain at least 1 Basic Pokémon.
** Previously, Fossil Cards (which are a different class of cards that can be played on the field like Basic Pokémon) were simply discarded when their Hit Points are depleted with no other penalty. Now, they count as a Knocked Out Pokémon, allowing the opponent to take a prize card (out of the 6 needed to win the game). This was because Fossil cards were rarely used for their intended purpose, which was to evolve them into usable Pokémons. Instead, they were treated as walls while the players prepared up their Pokémon from the (normally) unattackable Bench.

** After cards that easily Special Summoned multiple Token monsters like Dandylion or Grinder Golem got themselves on the banlist for providing easy Link Material for Link climbing shenanigans, subsequent Link Monsters would specify their (otherwise generic) Link Material requirements as either non-Token monsters, monsters with different names, or both. Any subsequent cards that churns out easy Tokens now prevents the player from Link Summoning for the rest of the turn or can't Link summon while the token is present.

** After cards that easily Special Summoned multiple Token monsters like Dandylion or Grinder Golem got themselves on the banlist for providing easy Link Material, subsequent Link Monsters would specify their (otherwise generic) Link Material requirements as either non-Token monsters, monsters with different names, or both. However, Link Monsters with higher Link Ratings that do not permit Tokens as Link Materials [[LoopholeAbuse can still be Link Summoned]] using Link Monsters with lower Link Ratings that ''do'', thus effectively bypassing the restriction.

** Later on, Fossil Cards, which are a different class of cards that can be played on the field like Basic Pokémon, count as a Knocked Out Pokémon when their Hit Points are depleted. Previously, they were simply discarded with no other penalty. This was because Fossil cards were rarely used for their intended purpose, which was to evolve them into usable Pokémon. Instead, they were treated as walls while the players charged up their Pokémon from the (normally) unattackable Bench. When the [[VideoGame/PokemonDiamondAndPearl Diamond and Pearl]] sets came out, there were now six different Fossil Cards: Dome Fossil, Helix Fossil, Claw Fossil, Root Fossil, Skull Fossil, and Shield Fossil, plus Old Amber, which has the same traits [[MyFriendsAndZoidberg but isn't a Fossil Card.]] A player could conceivably put 4 of each into a deck and litter their playing field with them, stalling out every match.

** If something is shown to be a GameBreaker, the most common means of addressing this is to release a new card a few sets later that serves as a hard counter to said GameBreaker. The most notable instance is the rise of Pokémon-SP, strong Basic Pokémon released alongside supplementary cards that allowed them to be directly searched out from a deck, shuffled around the table, gain additional attack effects, and so forth. This proved to dominate tournament play. The response was to release [[http://bulbapedia.bulbagarden.net/wiki/Machamp_(Stormfront_20) Machamp]] in the Stormfront set [[note]]Which actually came out ''before'' the set which introduced Pokémon-SP[[/note]], which has a low-cost attack that, if used on a Basic Pokémon, automatically knocks it out.
** Up until one point, if a Stadium card was in play, you could play another copy of the same one and discard the one already in play (which normally happens when another Stadium card is played). Later on, a new rule was added that prevents a player from playing a Stadium card that's the same as one already in play (such as your opponent's card), and said rule was added to all Stadium card text from there on in.

** In the ''VideoGame/PokemonBlackAndWhite'' sets, there was a Supporter card for Professor Juniper which had you discard your hand and draw 7 cards, which was reprinted towards the end of that generation. The first ''VideoGame/PokemonXAndY'' set gave us Professor Sycamore, a Supporter card with the ''exact same effect'', which meant you could have 8 copies of basically the same card in your deck. Being aware of this, Nintendo issued a rule stating you couldn't have more than 4 of any combination of Professor Juniper and Professor Sycamore in a deck.
*** Starting in the first ''VideoGame/PokemonSwordAndShield'' set, Supporter cards featuring Pokémon Professors are now called Professor's Research (which can feature a different Professor depending on the set), which have the same effect as above. Since a player can only have up to 4 copies of a specific named card in their deck, this limits the number of Pokémon Professor-related cards one can have in their deck.