Obvious Rule Patch / Pokémon

Pokémon has been subject to a few Obvious Rule Patches. They are ordered based on the generation they were introduced in.

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Generation I

• This is the purpose of the obedience mechanic. Once you unlock trading, there's really nothing stopping you from getting a high-level Pokémon from a friend. The obedience mechanic is designed to prevent you from using traded Pokémon to crush the game under your heel by making it so high-leveled Pokémon acquired from other Trainers have a very high chance of not listening to your commands until you collect the proper amount of Gym Badges or equivalents thereof.
  • In Sword and Shield, this mechanic was extended to the ability to catch high-level Pokémon outside of Raids due to the presence of the Wild Area where you can meet high-level wild Pokémon early.
  • Starting from Legends: Arceus, the catch penalty was mostly removed and obedience was changed so that it is based on the Pokémon's level at the time of being caught/traded rather than the current level, preventing legitimate outsider Pokémon from going disobedient when overleveled.
• Yellow changes the interaction with the Old Man in Viridian City who teaches you how to catch Pokémon from Red and Blue. Thus, he can no longer be used to trigger the MissingNo glitch.

Generation II

• With the introduction of the gender and breeding mechanics, in order to prevent people from breeding a bunch of starters, all of them have a 7:1 male-to-female ratio. However, as Technology Marches On, this effort was largely made obsolete by features such as Wonder Trade that allows people to obtain starters with relative ease, but the tradition persists to this day, leading to some awkwardness as starters with feminine designs like Delphox and Primarina being almost entirely male. Not to mention the fact that it was pointless to begin with, as they put Ditto right outside the Daycare and third gym in Gen II.
• Psychic-types in Gen I were very broken. Apart from its innate strengths, one of its intended weaknesses, Ghost, suffered from a programming error, which made Ghost completely ineffective on Psychic. When Gen II rolled around, aside from the nerfs to the type with the introduction of Dark and Steel, Ghost was correctly programmed so that it was properly effective against Psychic as intended.
• Unlike physical moves, special moves used the same stat for both attacking and defending. This meant that while an individual Pokémon could be good at using physical moves but bad at defending against them or vice versa, being good at using special moves automatically made a Pokémon good at defending against them. Add in the move Amnesia, which boosted the Special stat by two stages, and a Special-oriented Pokémon could quickly become a nightmare to take down. To make matters worse, at this point in the series, a move's type was what determined whether it was physical or special, and Psychic was one of the special types; see above for why this was such a bad thing. Gen II wisely split the Special stat into Special Attack and Special Defense, putting physical and special moves on more even footing.
• There are several moves that protect the user from taking damage that turn, most commonly Protect. Attempting to use Protect multiple turns in a row sharply slices its success rate to prevent indefinite stalling. Furthermore, similar guarding moves like Detect, Endure, and Spiky Shield all use the same mechanic, preventing alternating between multiple such moves to avoid the success rate reduction.
• Hyper Beam had a number of ways to bypass the cooldown turn after use, such as if it misses, the target faints, or it broke a Substitute. Come Gen II, all of these loopholes have been closed (except for missing) to give the move more of a downside.
• Struggle, the unique move reserved for when a Pokémon runs out of PP, behaved as a Normal-type move, which made it completely unable to affect Ghost-types. Later games would have it behave as a "typeless" move instead.

Generation III

• Shedinja, a Bug/Ghost type Pokémon, is a permanent One-Hit-Point Wonder to balance out its No-Sell ability, Wonder Guard. This blocks it from taking any direct damage that does not hit it super effectively, though it is still vulnerable to damage over time effects, damaging weather, abilities, and items. Since it has five weaknesses, it's also pretty easy to counter on that front, leaving it basically unusable apart from a few gimmicks like hard countering Kyogre. However, wouldn't it be nice if you could drop Wonder Guard onto, say, Sableye? Which until Gen VI^note Said Generation introduced the Fairy type, which is strong against Dark, while Ghost cannot resist it had no weaknesses at all? Nope, no can do! Moves like Role Play and Skill Swap are programmed to fail if used on this ability. The only way to get Wonder Guard onto another Pokémon is via Trace, or having Shedinja use Mimic to copy the move Entrainment, the former being only possible for your opponent and the second only being usable in Double Battles and requiring significant setup that can easily be stopped.

Generation IV

• Moves that take away a held item or otherwise supresses them (like Thief, Knock Off, and Magic Room) won't work on specific Pokémon holding items that they have unique interactions with (such as Arceus's Plates, Giratina's Griseous Orb, Genesect's Drives, and any Pokémon's specific Mega Stone), nor do they work on Z-Crystals. Stealing moves (and Fling) also won't work on those items if the user is a Pokémon that can use them (e.g. Arceus cannot steal an opponent's Plate or Fling its own Plate at them), and Z-Crystals are unaffected.
• Wobbuffet cannot attack directly, instead returning an opponent's damage back with Counter and Mirror Coat. However, when debuted in Gen II, Wobbuffet could not stop the opponent from just switching out over and over while it burned all of its PP. When Gen III introduced Abilities, Wobbuffet and its new baby form, Wynaut, got Shadow Tag, which prevents the opponent from switching out, to compensate; unfortunately, this had the unintended potential to end up in a draw if two Wobbuffets with Leftovers ended up facing off, as neither could switch out or do enough damage with Struggle to knock the other out, which happened in competitive matches. Gen IV would adjust Shadow Tag so that it also granted immunity against its own effect, and the self-damage calculation for Struggle got altered to make it depend on the user's maximum health rather than the damage dealt to the target.
• In Pokémon Diamond and Pearl, you received the National Pokédex upon seeing every Pokémon in the Sinnoh Pokédex. The idea was that you would only achieve this after beating the Elite Four, in which you can get Palkia (Diamond) or Dialga (Pearl) recorded into the Pokédex; but it was possible to achieve filling out the Sinnoh Pokédex through trading and thus get the National Pokédex before beating the game. Come Pokémon Platinum and in addition to seeing every Pokémon in the Sinnoh Pokédex, you also have to have beaten the Elite Four in order to get the National Pokédex.

Generation V

• Before this generation, a Pokémon holding a Focus Sash at full HP would be able to shrug off the entire sequence of a multi-hit move like Rock Blast or Pin Missile. Afterwards, it only protects against the first hit of such moves instead of the entire sequence.
• In this generation, there was a glitch involving the new move Sky Drop. The move makes one Pokémon take another into the air (and then drop it for damage), and when a Pokémon is in the air, it cannot move or be hit (except by moves that can hit airborne opponents, like Thunder). The move Gravity makes Flying-types or levitating Pokémon come to the ground (this meaning they can be hit by Ground-type moves), but in a double battle, if one of your Pokémon uses Sky Drop and the other then uses Gravity, both Pokémon will come to the ground... except while your Pokémon can move, theirs is treated as being in the air and cannot move, at all, until they faint through airborne-hitting moves. The Obvious Rule Patch? Nintendo banned Sky Drop in random online battles. Gen VI later adjusted Sky Drop, patching this glitch.

Generation VI

• In Gens IV and V, there were problems with players disconnecting to preserve their win-loss record. Beginning with Pokémon X and Y, however, disconnecting on players will count as a loss to the player who shut their game off.

Generation VII

• Mega Rayquaza is different from other Mega Evolutions in that Rayquaza doesn't need to hold a specific Mega Stone to transform, and can therefore hold any item it wants. When Pokémon Sun and Moon introduced Z-Moves (powerful attacks that can only be used once), a Rayquaza holding a Z-Crystal cannot Mega Evolve, preventing it from using both gimmicks at the same time.
  • The games have gone out of their way to ensure a Mega-Evolved Pokémon can't use a Z-Move under any circumstances. Most notable is that, if a Pokémon holding a Z-Crystal uses Transform or the Imposter ability to transform into a Mega Pokémon, if it tries to use a Z-Move, it'll say that there's no compatible move, even if it knows a move of a matching type.
• Dark Void is a very powerful move in Double Battles (putting both opposing Pokémon to sleep), normally mitigated by it being exclusive to Darkrai, a Pokémon normally banned in competitions. However, Smeargle can learn any move in the game through Sketch, and as a result Dark Void Smeargle ran rampant through the Video Game Championships scene for years, annoying players to no end due to how difficult it was to counter. Pokémon Sun and Moon not only nerfed Dark Void's accuracy to 50%, but made it automatically fail if used by any Pokémon other than Darkrai.
• While a player can have both a Dusk Mane Necrozma and a Dawn Wings Necrozma in their party in Pokémon Ultra Sun and Ultra Moon, only one of them can transform into Ultra Necrozma per battle; transforming one will prevent the other from doing so, even if the transformed Necrozma faints.
• Starting from the Let's Go Pikachu and Eevee, the Pokémon Storage System can be accessed at any time, instead of needing to return to a Pokémon Center. Accordingly, Pokémon deposited into a Box will not be automatically healed (as was the case in previous generations except in Gen I).

Generation VIII

• Pikachu and Eevee with the Gigantamax factor can't be evolved, so Pokémon HOME will not allow such Pikachu and Eevee to be moved to other games either, preventing the player from obtaining Gigantamax factor Raichu and Eeveelutions with no corresponding form. The same restriction applies to Duraludon, despite its evolved form Archaludon not being introduced until Pokémon Scarlet and Violet, meaning it couldn't be moved back after evolving either way.
• Mimikyu's Disguise Ability meant that it completely shrugs off one attack per battle until it faints, regardless of power. This means that giving it the Focus Sash at full HP will allow it to survive at least two hits that would have knocked it out. In this generation afterwards, Mimikyu loses 1/8 of its max HP upon tanking the damage with Disguise, removing its synergy with Focus Sash.

Generation IX

• Adaptability is an Ability that was introduced all the way back in Gen IV and increases the STAB multiplier from 1.5x to 2x for moves of the same type as the user. Terastallization is also a mechanic that does the same if the user Terastallizes into (one of) its same type(s). Should you attempt to Terastallize a Pokémon with Adaptability to one of its types (e.g. Tera Water Crawdaunt), instead of both multipliers stacking, the resulting boost is 2.25x instead, preventing such mons from becoming obscenely powerful wallbreakers.
• When the DLC for Pokémon Scarlet and Violet was released, players discovered a duplication exploit that involved getting a wild Smeargle to use Transform on a large Pokemon. This was patched by making it so that Smeargle could not use Transform in wild battles - but Ditto and Mew still can, and Smeargle can still use the move in trainer battles.

Virtual Console releases

• The Virtual Console release of Pokémon Red and Blue does not allow Save States (a standard feature for other Virtual Console games released on the Nintendo 3DS) to prevent players from cloning Pokémon, and prevents players from transferring Mew obtained through a glitch. In addition, all Pokémon transferred have their Hidden Abilities, otherwise people could use an Ability Capsule on Machamp to give it No Guard to ensure Fissure (which the TM for only existed in Gen I) would always land.

Smogon

• When Smogon decided that Mega Rayquaza was too much of a Game-Breaker even for the Uber tier, they created the "Anything Goes" tier so they had somewhere to ban it to. The rules for Anything Goes are just what they sound like — no bans, no restrictions... except that even in Anything Goes, the "Endless Battle" clause forbids movesets designed to extend the battle indefinitely just to piss the other player off.
• The Endless Battle Clause itself had to be modified several times to account for certain creative types finding ways around the convoluted ban, which at its core involved a Leppa Berry^note Restores 10 PP to any move that runs out of PP, the move Recycle^note Recovers a used item, such as a Leppa Berry; in this case allowing infinite PP restoration, and some method of keeping the opponent from suiciding from Struggle recoil, of which there are shockingly many methods.
• Pokémon Black and White gave Politoed and Ninetales, respectively, the abilities Drizzle and Drought, which summon permanent rain/sun; this gives numerous bonuses to certain Pokémon, including increasing the power of Water-/Fire-type moves and activating certain abilities, most notably Swift Swim and Chlorophyll, which double the Pokémon's speed under these conditions. Another ability, Sand Rush, was also introduced, which doubles speed in a sandstorm. The problems come from how, at the beginning of Black and White, Politoed plus Swift Swim sweepers ran wild over the game. Smogon later came up with a complex ban: Politoed could not be on a team with a Swift Swim Pokémon. However, this has the opposite effect, on which players would then bring their own Swift Swim Pokémon to counter such teams, something that repeated for Chlorophyll and Sand Rush. The rule later extended to banning climate Speed-boosting Abilities.
• Smogon tier lists are usually determined by usage. The more a Pokémon is used, the higher the tier it is in, the logic being that players will use the better more often. However, there were Pokémon that were not used enough to be useful in a higher tier but came to utterly dominate some lower tier. For example, in Black and White, no one would use Kyurem in Overused, but it completely destroyed most Pokémon in Underused. Smogon created "borderline" (now called ban lists) for Pokémon that are too good to be used in one tier but not used enough to be placed into a higher tier.
• Originally, tier lists were determined only by usage. After a user named "ihabt" decided to use several Never Used Pokémon in Rarely Used with terrible movesets and setups frequently with the intent of moving them up to Rarely Used, Smogon changed things so that such a Pokémon can't just be used in a specific tier, it needs to be viable and capable of winning enough battles in that tier as well.

Self-imposed challenges

• Some Nuzlocke runs of later generations will have additional rules to account for new mechanics not present in Gen III, where the Nuzlocke Comics originated. For example, Pokémon Omega Ruby and Alpha Sapphire introduced the DexNav and sneaking through grass, which would make the Nuzlocke rule of "You can only catch the first encounter on a route" a complete joke since getting a really good first encounter would be incredibly easy. Possible rule patches for this would be to either forbid using the DexNav entirely, forbid sneaking through grass to get to a detected Pokémon until you're right next to it, or consider the first detected Pokémon the first encounter (so if it's not ideal, too bad, and if you give it up, you can't try again).