History EarlyInstallmentWeirdness / PokemonRedAndBlue

** Due to how infliction for status effects worked, damaging moves that inflict the Paralysis, Burn, and Freeze status effect could not inflict their status on Pokémon of the same type as the move. Which meant Normal-types couldn't get any status ailment from Tri-Attack or paralysis from Body Slam, Ghost-types wouldn't get paralyzed by Lick, etc. This did not apply to pure status moves though, meaning Thunder Wave could still paralyze Electric-types. The Poison status in general was also exempt from this, meaning the Bug-type move Twineedle would still poison Bug Pokémon, but not Poison-types (who were immune to the status even in Gen I). Gen II would fix this issue.

** Psychic-type Pokémon. Thanks to a programming error, they're immune rather than weak to Ghost attacks in Generation I, leaving them with a weakness to only Bug-type. Not that it would have mattered much if the error wasn't present, as neither typing had much in the way of offense power during this gen. The only damaging Ghost-type attack that wasn't a FixedDamageAttack was Lick (which was only 20 base power at the time) and the only Ghost-types in the game (the Gastly line) were weak to Psychic thanks to being dual-type Poison; meanwhile, the Bug-type attack Leech Life was only 20 base power as well, leaving the player with only Pin Missile and Twineedle... which the most powerful Bug-types in the game couldn't even learn, and the ones that could were also dual-type Poison.

** Steel, Dark, and Fairy don't yet exist as typings. Steel and Dark were added in Gen II to nerf Psychic-type Pokémon (the former resists Psychic damage, while the latter is immune). Fairy would be added in Gen VI to nerf Dragon and buff Poison.

* The Pokémon used by all trainers, including important trainers such as Gym Leaders, the Elite Four, and the Rival, will have the four latest moves that said Pokémon would learn at their level, just like a wild Pokémon would.[[note]]Though the last Pokémon of a Leader will at least also know the TM move said Leader would give you as a reward.[[/note]] When combined with the generally barren natural learnsets of Gen I covered in the "Moves and Items" section, you get some ridiculous and rather ineffective movesets, even with endgame trainers. This includes Giovanni's Rhydon only knowing a single damaging move in Stomp (which was Normal type at that), and ''two'' OneHitKill moves; Lorelei's Slowbro not only still having Water Gun, but also being its ''only'' damaging move.; Lance's Aerodactyl and Dragonite only having Normal-type moves, meaning that they'd be unable to harm a Ghost-type Pokémon; and Champion Blue's Exeggutor only knowing ''three'' moves, with both of its only damaging moves again being Normal type (Stomp and Barrage). In later games, Pokémon used by Gym Leaders and other important trainers would either have customized moves involving plenty of [=TMs=] and Egg Moves that follow a specific strategy[[note]]for example, Flannery's Slugmas know both Sunny Day and Light Screen to set up her Torkoal to sweep your team with Sunny Day-empowered Overheats while Sunny Day and Light Screen protect it from Water-type moves[[/note]] or at least have an assortment of varied damage dealing moves with type coverage in mind[[note]]For example, Cynthia's Roserade knows Shadow Ball in case you want to bring it down with a Psychic Pokémon, and her Garchomp knows Brick Break in the likely case you want to send an Ice-type[[/note]]. In fact, this was changed as soon as ''Yellow'': Giovanni's Rhydon knows Rock Slide and Earthquake, two powerful STAB moves, same with Lorelei's Slowbro knowing both Psychic and Surf, while Lance's Aerodactyl knows Flying-type moves and his Dragonite has the terrifying combo of [[FireIceLightning Fire Blast, Thunder and Blizzard]].

* Pokémon names are consistently pluralized with an "s" at the end. For example, Weezing's Pokédex entry mentions that "2 Koffing''s'' can fuse into a Weezing over many years". Later ''Pokémon'' media has the plural forms of Pokémon names the same as the singular, as with moose and sheep. The rare instance of an exception to this rule [[{{Pluralses}} can be considered an error]].

* Pokémon names are consistently pluralized with an "s" at the end. For example, Weezing's Pokédex entry mentions that "2 Koffing''s'' can fuse into a Weezing over many years". Later ''Pokémon'' media has the plural forms of Pokémon names the same as the singular, much like moose or sheep -- rare exceptions to this rule [[{{Pluralses}} can be considered errors]].

* Pokémon names are consistently pluralized with an "s" at the end. For example, Weezing's Pokédex entry mentions "2 Koffing''s'' can fuse into a Weezing over many years". Later ''Pokémon'' media has the plural forms of Pokémon names the same as the singular, much like moose or sheep; the rare exceptions to this rule [[Pluralses can be considered errors]].

* Pokémon lay eggs... except that one of the [[ApocalypticLog journal entries]] found in the Pokémon Mansion says "Mew gave birth. We named the newborn Mewtwo." This was unchanged in the remakes, which feature breeding, but the ''Let's Go!'' games instead say they "obtained a new Pokémon" from Mew.

* When trying to catch Legendaries or [=Pokémon=] in the Safari Zone, expect to see "You missed the [=POKéMON!=]" instead of the standard "Oh, the [=POKéMON=] broke free!". Unlike later games, using Poké Balls has four different failure messages instead of three; the first and worst failure message being that the Pokémon [[NoSell dodged the ball entirely]]. Additionally, the number of times the ball shakes on a failed capture is always the same, loosely based on an approximation of the odds of catching the Pokémon. Later games have the amount of shakes be independent of the likelihood of capture, using "shake checks" on failed captures to determine how many times the ball should shake.

* ''Pokémon Yellow'' is unique among Pokémon games for several reasons. Firstly, it's a ''fourth'' version made after an UpdatedRerelease third version (Japanese ''Blue'') was already created, something which would never happen again. Secondly, its biggest design differences is based on the anime, meaning that it is a rare example of [[CanonImmigrant the mainline games using elements of the anime]] and effectively serving as an advertisement for the anime instead of the other way around. Thirdly, it's the only main series game that doesn't give you a choice of starter until ''VideoGame/PokemonLetsGoPikachuAndLetsGoEevee'', which are remakes of this title.

* You are unable to catch any Pokémon if your current PC box is full, requiring you to manually switch to a new one. You also aren't told when you've filled up your box, meaning you can try to catch a Pokémon only to get a sudden text box saying that you can't. In Gen II, Bill call you whenever you filled up a box, while Gen III onwards automatically switch boxes without you having to do anything.

* Using Rage meant that you were locked into using the move until the end of the battle. From Gen II onward, this was changed to allow for the player to have control again on the next turn.

* While still working out to have the same level of effect as [=IVs=] in later gens, Individual Values are on a scale of 0 to 15 rather than 0 to 31; the only other game in the franchise to use a 0-15 scale is ''VideoGame/PokemonGo''. Meanwhile, the HP IV is dependent on other stats; all future games, including ''GO'', have HP determined separately.

* The Silph Scope is required in order to see and identify Marowak's ghost in Pokémon Tower so you can progress with the plot. Without it, Marowak's ghost effectively blocks you from reaching the final room, as your Pokémon will be too scared to attack it.[[note]]Which makes very little sense, as you have to fight a bunch of ghost Pokémon to get there in the first place -- while your mons reacted the same way to the ''wild'' ghosts, they had no such qualms about the ghosts held by the local ''Trainers''[[/note]] While the concept of needing to uncover the actual form of a Pokémon would reappear in future entries, the idea of your Pokémon being "too scared" to attack an opponent is exclusive to these games and their remakes.

* Numerous trainers are depicted as carrying whips (Cooltrainers, Tamers, Rocket Grunts, Cue Balls, Sabrina) as a holdover from when Pokémon were intended to be treated in-universe as more violent monsters rather than powerful pets. All future games removed them, except for the Tamer class in the remakes.

** From Gen II onward, each box legendary would have a [[SecretArt signature move or ability]] that only it could have (for example, Ho-oh and Lugia got the exclusive moves Sacred Fire and Aeroblast, respectively). It would take until Gen V for a first generation legendary to get their own signature move, that being Mewtwo with Psystrike.

* Hyper Beam would skip the recharge turn if it knocked the opponent out, making it a high risk, high reward move that sees extensive use in competitive play. ''Pokemon Stadium'' would remove this quirk and force the recharge turn regardless of if the opponent faints, which all future Gens would keep for Hyper Beam and all its deriatives, making the move notoriously impractical.

* The Silph Scope is required in order to see and identify Marowak's ghost in Pokémon Tower so you can progress with the plot. Without it, Marowak's ghost effectively blocks you from reaching the final room, as your Pokémon will be too scared to attack it.[[note]]Which makes very little sense, as you have to fight a bunch of ghost Pokemon to get there in the first place -- while your mons reacted the same way to the ''wild'' ghosts, they had no such qualms about the ghosts held by the local ''Trainers''[[/note]] While the concept of needing to uncover the actual form of a Pokémon would reappear in future entries, the idea of your Pokémon being "too scared" to attack an opponent is exclusive to these games and their remakes.

* The covers for the Gen 1 games (save for Yellow) had the third stage evolution for the starter Pokemon on them. Starting with Gen 2 and onward, the covers would have a Legendary Pokemon on it.

* In general, Normal seems to have been the default assumption for types in general, as opposed to future generations, where it tends to be treated as one type among many.

* Several Pokémon did not learn any attacking moves of their own type through leveling up. Pinsir and Scyther didn't learn any Bug moves, Voltorb and Electrode didn't learn any Electric moves, Rhyhorn and Rhydon didn't learn any Rock ''nor'' Ground moves, etc. [=TMs=] were able to provide for some, but the aforementioned lack of variety still left certain Pokémon with no options. Gen II began to expand move pools and offer more varied [=TMs=], and it is now unheard of for a Pokémon not to naturally learn at least one move of its own typing.

** If a Pokémon uses Selfdestruct or Explosion on an opponent's Substitute and breaks it, the exploding Pokémon will not faint or take any self-inflicated damage at all (though its sprite will still disappear). Similarly if a Pokémon breaks an opponent's Substitute with Hyper Beam they will not have to recharge the next turn.

* Gen I is the only generation with no female protagonist. Starting with Kris in Gen II's ''Crystal Version'', every game has had both a male and female option. Early official art shows that a female protagonist [[WhatCouldHaveBeen was planned]], but was ultimately scrapped (likely due to no space being left on the cartridge for her). Her design would be see use in the spin-off material like ''Manga/PokemonAdventures'' before seeing use in the GBA remakes as female player option (Leaf), and in ''Let's Go'' as an NPC (Green).

* When you trade a Pokémon, the background music still plays, when later generations has the evolution theme play in its place.

* The Silph Scope is required in order to see and identify Marowak's ghost in Pokémon Tower so you can progress with the plot. Without it, Marowak's ghost effectively blocks you from reaching the final room, as your Pokémon will be too scared to attack it.[[note]]Which makes very little sense, as you have to fight a bunch of ghost Pokemon to get there in the first place -- while your mons reacted the same way to the ''wild'' ghosts, they had no such qualms about the ghosts held by the local ''Trainers''[[/note]] The concept of needing to uncover the actual form of a Pokémon would reappear in future entries, the idea of your Pokémon being "too scared" to attack an opponent is exclusive to these games and their remakes.
* How this game handles Ghost Pokémon is very different from any other. The Silph Scope is required to see them in the wild, otherwise they appear as "ghosts" and cannot be interacted with. The only trainers that use them are Mediums, and most of them are being outright possesed by their own Gastly. Gen 2 put them more in line with the other types, even giving them a relatively normal gym.

* The Pokémon League is implied to be a new thing; most players interpreted Lance's dialogue to mean that [[TheRival your rival]] was the first Trainer to ever beat the Elite Four, though he never ''[[ExactWords directly]]'' says this. ''Let's Go Pikachu/Eevee'' would have Lance explictly say that while your rival wasn't the first to beat the Elite Four, this is the first time that fighting the previous Champion is mandatory.

* In the Kanto games, Lt. Surge mentions a GreatOffscreenWar that happened that he was involved with. The war has never been clarified upon since. Considering the original games were much more Earth-like, he's likely discussing a real world war (likely UsefulNotes/GulfWar, the most recent war involving the US at the time).

* X Accuracies in Gen I and II allow your Pokémon to ignore accuracy checks entirely, making even OneHitKill moves always hit. This was severely nerfed in future games, instead increasing accuracy by one or two stages.

** Dig is 100 base power; Gen II would lower it to 60 BP, while Gen IV would raise up to 80 BP.
** Blizzard has 90% accuracy, instead of the 70% it would have in all future Gens.

** Dragonite similarly couldn't learn Fly despite even its sprite depicting it flying, and it took until ''Gold'' and ''Silver'' to correct this. Dragonite didn't get Wing Attakc either, which combined with the fact that Dragon Rage was the only Dragon move, left Dragonite with no STAB moves in its debut generation.