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Throughout the franchise, the design of some Pokémon received various amounts of changes. Some were temporary, only lasting for one or two games, while others remained for a fair bit longer, causing a disconnect between the video games and other Pokémon-related media.

Overview

The first few generations are interesting due to the sprites having been made before the artwork^[1], rendering the "errors" and other oddities as nothing more than design revisions.

Generation I, for instance, had the original designs tweaked in some places, with Pokémon Blue giving the original roster new sprites, though the back sprites were consistently left untouched. Pokémon Yellow would later update the front sprites once more, this time explicitly basing them after the Pokémon's appearance in the animated series.

In Pokémon Gold and Silver, the sprites for the Kanto Pokémon are mainly based on the contemporary Red and Blue artwork, with some of the new elements tentatively introduced there (such as Nidoqueen's fangs) making a return. Much like with Yellow, Pokémon Crystal later changed a good handful of sprites, using each Pokémon's respective artwork as a basis. This mostly affected the Johto Pokémon, and this time around the back sprites were also updated here and there.

Pokémon Ruby and Sapphire is likely when the majority of artwork was starting to be drawn before the sprites, leaving most of the inconsistencies to be minor in comparison to previous generations. However, many of the Generation I and II Pokémon's sprites were either copied directly from Crystal or based on outdated artwork, as those Pokémon had yet to be redrawn for FireRed and LeafGreen or HeartGold and SoulSilver.

List of sprite discrepancies

Sprite discrepancies due to design revisions

Generation I Pokémon

No.		Game(s)	Reason
001	Bulbasaur	Generation I core series	Originally had round ears instead of triangular ones.
002	Ivysaur	Generation I core series Generation II core series Pokémon Pinball	Originally had a stalk, round ears instead of triangular ones, and two leaves instead of four. Red and Blue changed the ears, while Yellow changed the leaf count. The two-leaf design returned in Generation II, though only on the front sprites. The Generation I back sprite features a tail. The two-leaf design was reflected in its Red and Blue artwork.
003	Venusaur	Generation I core series Generation II core series Generation III core series	Originally had spots, round ears instead of triangular ones, two leaves instead of four, and five petals instead of six. Red and Blue changed the ears and leaf count, while Yellow removed the spots and changed the petal count. The petal count was not carried forward after this, however, as it only appeared on the Silver front sprite before Generation IV. The Generation I back sprite features a tail, while the Generation II, Ruby, Sapphire, and Emerald back sprites feature a rounder petal shape. The five-petal design was reflected in its Red and Blue artwork.
004	Charmander	Generation I core series	Originally had a dorsal ridge. This was reflected in its Carddass artwork.
005	Charmeleon	Generation I core series	Originally had a horn instead of a head protrusion.
007	Squirtle	Generation I core series	Originally had a different plastron design, cheek patterns, and a fluffier tail resembling Wartortle's.
009	Blastoise	Generation I core series Generation II core series Generation III core series Pokémon Pinball	Originally had different cannon cover designs. It was first changed in Yellow, and then to its current design FireRed and LeafGreen, though only on the back sprite.
010	Caterpie	Generation I core series Pokémon Pinball	Originally lacked the pattern on its body.
011	Metapod	Generation I core series	Originally had crosshair-shaped eyes instead of droopy ones.
012	Butterfree	Generation I core series	Originally had differently shaped wings.
014	Kakuna	Generation I core series	Originally lacked pupils. The Red and Blue sprite has its pincers extended, as seen in its Carddass artwork.
016	Pidgey	Pokémon Pinball	Features much longer eyebrows, as seen in its Red and Blue artwork.
018	Pidgeot	Generation II core series	Features Pidgeotto's tailfeather coloration, as seen in its Red and Blue artwork.
019	Rattata	Generation I core series	Originally had a white tail.
020	Raticate	Generation I core series Ruby and Sapphire Emerald	Originally had four fingers on each hand instead of three. This was changed in Yellow, but returned in Ruby, Sapphire, and Emerald.
022	Fearow	Generation I core series	Originally had three talons instead of four.
024	Arbok	Generation I core series	Originally had wave-shaped markings on its back.
025	Pikachu	Red and Green Red and Blue	Originally had a white belly. This was reflected in its Carddass artwork.
029	Nidoran♀	Generation I core series Pokémon Pinball	The Generation I back sprite features different spike placement. Pinball features a tail, as seen in its Red and Blue artwork.
030	Nidorina	Generation I core series	Back sprite depicts it as lacking spikes altogether.
031	Nidoqueen	Generation I core series Gold Crystal Generation III core series	Originally had two rows of spikes. The Generation II and III front sprites feature fangs, as seen in its Red and Blue artwork.
033	Nidorino	Generation I core series	Originally had a tail, as well as a line running through the its inner ear. The back sprite features a dorsal ridge.
034	Nidoking	Generation I core series	Originally had two toes on each foot. The back sprite features two rows of spikes.
035	Clefairy	Generation I core series Gold and Silver	Originally had pawpads, a different ear shape, and back spikes. Red and Blue changed the ear shape and changed the back spikes to wings, while Crystal removed the pawpads.
036	Clefable	Generation I core series	Back sprite features a different ear shape.
037	Vulpix	Generation I core series	Originally had different crest designs. The back sprite features a completely different design, while the Red, Green, and Blue front sprite resembles the current one, albeit with two curls instead of three.
038	Ninetales	Generation I core series Generation III core series Pokémon Pinball	Originally had a different crest design. The Generation III and Pinball front sprites lack differently-colored tail tips, as seen in its Red and Blue artwork.
040	Wigglytuff	Generation I core series Gold Crystal Ruby and Sapphire Emerald Pokémon Pinball	Originally had a white hair tuft instead of a pink one, as well as a stomach pattern that doesn't reach over the mouth. The Generation I back sprite and Red and Blue front sprite have pink eartips. Red and Blue changed the stomach pattern, while Yellow changed the hair tuft and eartips. Some of these traits returned in both Generation II and III.
042	Golbat	Red and Blue	Features a long tongue only ever seen again in spin-off games.
045	Vileplume	Generation I core series	Back sprite depicts its flower without white spots.
049	Venomoth	Generation I core series	Originally had a different wing pattern, triangular pupils, and lacked mandibles.
052	Meowth	Generation I core series	The backs of its ears were originally black instead of cream. This was reflected in its Red and Blue artwork.
053	Persian	Generation I core series	Originally had dark paw and tail accents, and the backs of its ears were black instead of cream.
055	Golduck	Red and Green Red and Blue Pokémon Pinball: Ruby & Sapphire	Originally had four fingers on each hand instead of three. This was reflected in its Red and Blue artwork.
056	Mankey	Generation I core series	Originally lacked dark paws and had a white tail tip.
061	Poliwhirl	Red and Green Red and Blue Generation II core series Ruby and Sapphire Pokémon Pinball	Was often depicted with gloves instead of mittens, as seen in its Red and Blue artwork.
062	Poliwrath	Red and Green Generation II core series Ruby and Sapphire	Originally had four fingers on each hand instead of three. This was reflected in its Red and Blue artwork.
063	Abra	Generation I core series	Originally had a segmented tail which lacked the dark ring near its tip, as well as a joined back plate instead of separate shoulder plates.
064	Kadabra	Generation I core series	Originally had a segmented tail which lacked the dark ring near its base, a protrustion on the back of its head, and four fingers on each hand instead of three. It also lacked the markings on its stomach and head.
065	Alakazam	Generation I core series	Originally had a Star of David on its forehead, as well as a joined back plate instead of separate shoulder plated.
066	Machop	Generation I core series Generation II core series HeartGold and SoulSilver	Originally had four fingers on each hand instead of five. Its head crest was also made up of three segments of different lengths. The crest was changed in Red and Blue, while the finger count is difficult to tell. It remained until at least HeartGold and SoulSilver.
067	Machoke	Generation I core series Gold Crystal Generation III core series	Originally had four toes on each foot instead of five, and its head crest descended into a mullet. The Red and Green and Red and Blue front sprites both feature a four-part crest. These crest oddities were removed in Yellow, but the toe count remained unchanged until Generation IV, except for an error in Silver.
068	Machamp	Generation I core series Gold Crystal Generation III core series	Originally had four fingers on each hand instead of five. It also had different head ornamentation. Instead of a three-part crest, it has a single ridge accompanied by two horns. The Generation I back sprite and Red and Blue front sprite lack defined lips. The Gold, Crystal, and Generation III sprites lack a belt, as seen in its Red and Blue artwork.
073	Tentacruel	Generation I core series	Back sprite features a line which connects the two large gems.
075	Graveler	Pokémon Pinball: Ruby & Sapphire	Features dark-colored fingers, as seen in its Red and Blue artwork.
076	Golem	Generation I core series Generation II core series Generation III core series	Originally looked much friendlier as it lacked claws, sharp teeth, angry eyes. The Yellow, Generation II, and Generation III front sprites feature it with four toes on each foot instead of five, as seen in its Red and Blue artwork.
078	Rapidash	Generation I core series	Originally had a spiraling horn instead of a smooth one.
079	Slowpoke	Generation I core series Gold Japanese Silver Crystal	Originally had two toes on its hind feet, a striped underbelly, and the backs of its ears were curled instead of smooth. The toes were changed in Red and Blue, and the ears were changed in Gold and Silver. The underbelly was removed in the International versions of Silver, but remained in all releases of Gold and Crystal.
080	Slowbro	Generation I core series Generation II core series Ruby and Sapphire Emerald	The backs of its ears were originally curled instead of smooth. The Ruby, Sapphire, and Emerald front sprites feature a spiraling Shellder, as seen in its Red and Blue artwork.
082	Magneton	Generation II core series Generation III core series Pokémon Pinball	Features nine screws instead of seven, as seen in its Red and Blue artwork.
083	Farfetch'd	Generation I core series Generation II core series Generation III core series	Originally had stripes on the tips of its wings. This was reduced to a single stripe in Generation II. It was first removed on Crystal's front sprite, but it returned in Ruby, Sapphire, and Emerald. It was removed again in FireRed and LeafGreen, though only on the front sprite.
084	Doduo	Red and Green HeartGold and SoulSilver	Originally had a different talon arrangement, with three in front and one in the rear.
085	Dodrio	Red and Green Red and Blue	Originally had three talons on each foot instead of four. Additionally, each head had the same expression. The talons were changed in Red and Blue, while the faces were changed in Yellow. The three-talon design was reflected on its Red and Blue artwork.
092	Gastly	Generation I core series	Originally had a less defined body, as well as more defined eyelashes.
093	Haunter	Generation I core series Generation III core series Pokémon Pinball	Originally had four fingers on each hand instead of three. The finger count was changed in Yellow, but it returned in Generation III. The Generation I back sprite features a different lower body design.
094	Gengar	Generation I core series	Back sprite depicts it as lacking spikes altogether. This is reflected in the game intro of Red and Green.
096	Drowzee	Generation I core series	Originally had brown feet and a more compact dark pattern.
098	Krabby	Generation I core series	Originally had two circular lower back protrusions.
099	Kingler	Generation I core series	Originally had relief on its back, four head spikes instead of six, and the larger pincer was on the opposite side.
100	Voltorb	Red and Blue Gold Crystal Pokémon Pinball: Ruby & Sapphire	Originally had a small circle on its lower half, as seen in its Red and Blue artwork.
101	Electrode	Generation I core series Pokémon Pinball	Originally had a small circle on its upper half. Pinball instead has this circle on its bottom half. The bottom half circle design is reflected in its Red and Blue artwork.
103	Exeggutor	Generation I core series Generation II core series Ruby and Sapphire Emerald	Originally had a fourth head on its back.
105	Marowak	Generation I core series	Originally had a series of back spikes.
106	Hitmonlee	Generation I core series Generation II core series Generation III core series	Originally had diamond-shaped sclera.
107	Hitmonchan	Generation I core series	Originally had a joined back plate, as opposed to separate shoulder plates.
108	Lickitung	Generation I core series Generation II core series Ruby and Sapphire	Originally had a split tongue, a slightly different knee pattern, and eyebrow patterns. Interstingly, its Red and Blue artwork depicts it with actual eyebrows. The tongue and knee pattern were changed in Red and Blue, while the eyebrow patterns were changed in FireRed and LeafGreen.
109	Koffing	Red and Green Silver	Originally had smoke hands. The Silver sprite features a two-toothed skull pattern, as seen in its Red and Blue artwork.

Sprite discrepancies due to artist error

Generation I Pokémon

No.		Game(s)	Reason
007	Squirtle	Pokémon Pinball	Mistakenly features Wartortle's plastron design.
008	Wartortle	Red and Blue	Bottom section of the plastron is split in two.
011	Metapod	Yellow Generation II core series Ruby and Sapphire Emerald	The Yellow front sprite mistakenly has its eyes placed on its back, as seen in artwork for Pokémon the Series. The Generation II back sprite lacks the ridge on its back and features an extraneous line connecting the eyes. The ridge was added in Ruby and Sapphire, while the line was removed in FireRed and LeafGreen.
017	Pidgeotto	Crystal	While properly colored in Gold and Silver, its beak was recolored to brown, though only on the front sprite.
024	Arbok	Generation V core series	Lacks a tail segment when compared to its back sprite.
025	Pikachu	Generation II core series	Tail is misshapen.
029	Nidoran♀	Red and Blue Diamond and Pearl Pokémon Pinball	The Red and Blue front sprite lacks a horn. The Diamond and Pearl back sprite has a misshapen inner ear. The Pinball sprite lacks whiskers and has spikes in its ears similar to Nidoran♂.
035	Clefairy	Generation II core series Generation III core series Diamond and Pearl Platinum	The Generation II and III back sprites mistakenly have Clefable's tail. The Generation III, Diamond, Pearl, and Platinum front sprites have ears with brown undersides instead of black. This was corrected on Platinum's back sprite and from HeartGold and SoulSilver onwards.
036	Clefable	Generation I core series Generation III core series Generation IV core series Pokémon Pinball	The Red and Blue front sprite and Pinball sprite mistakenly have Clefairy's cheek patterns. The Generation III and IV back sprites feature a heart-shaped pattern on its wings.
037	Vulpix	Red and Green Pokémon Pinball	Has five tails instead of six. Pinball also has two crest curls instead of three. Note that the two curls on the Red and Green sprite are an earlier design and not a mistake.
038	Ninetales	Yellow	Has too many tails.
041	Zubat	Gold	Membrane is visible on the back of the wing, which is only the case with Golbat's wings, not Zubat's.
053	Persian	Red and Blue	Ears are pointy instead of round.
055	Golduck	Crystal	While properly colored in Gold and Silver, its beak was recolored to light blue.
056	Mankey	Red and Blue	Fur is smooth rather than unkempt.
060	Poliwag	Gold Crystal Generation III core series	Intestines are too small and thick.
062	Poliwrath	Diamond and Pearl	Lacks intestines.
066	Machop	Diamond and Pearl	Back of the crest is too rounded.
067	Machoke	Generation II core series Generation III core series	The Silver front sprite mistakenly has Machamp's toes, while the Generation II back sprite has a crest that is too rounded in the rear. The Generation III front sprites have four fingers on each hand instead of five.
068	Machoke	Diamond and Pearl	Back of the crest is too rounded.
074	Geodude	Red and Blue	Has four fingers on each hand instead of five.
079	Slowpoke	Yellow	Lacks the white tip at the end of its tail.
080	Slowbro	Generation III core series Generation V core series	The Generation III back sprites lack spots on Shellder. The Generation V front sprite is missing an eye on Shellder.
083	Farfetch'd	Gold	The insides of its wings are drawn as if they are the outsides.
084	Doduo	Red and Blue FireRed and LeafGreen	Has three talons on each foot instead of four.
085	Dodrio	Gold	Mistakenly uses Doduo's talon arrangement. Additionally, the tips of its tailfeathers lack a highlight.
091	Cloyster	Red and Blue	Features a horizontal shell instead of a vertical one. Additionally, it is missing its horn.
094	Gengar	Generation II core series Generation III core series Diamond and Pearl	Spikes on its back aren't connected and have a different shape. This is reflected in the game intro of FireRed and LeafGreen.
096	Drowzee	Red and Blue	Has five fingers on each hand instead of three.
099	Kingler	Red and Blue	Has a large pincer on both sides.
102	Exeggcute	Red and Blue	Central egg is way larger than it should be.
105	Marowak	Gold Ruby and Sapphire Diamond and Pearl	Missing its thumb spike.
106	Hitmonlee	Generation I core series Generation II core series Platinum	Red and Green is missing the ankle pad on the left foot, Red and Blue is missing ankle pads entirely, Yellow and Generation II have misplaced ankle pads on the outside of the left feet, and Platinum has ankle pads on both sides of the left foot.
109	Koffing	Red and Blue	Skull and crossbones marking is above its face.

List of model discrepancies

Model discrepancies due to design revisions

No.		Game(s)	Reason
031	Nidoqueen	Pokémon Stadium series Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Features fangs, as seen in its Red and Blue artwork.
040	Wigglytuff	Pokémon Stadium series	Stomach pattern doesn't reach over its mouth, as seen in its Red and Blue artwork.
062	Poliwrath	Pokémon Stadium series Pokémon Colosseum Pokémon XD: Gale of Darkness	Has four fingers on each hand instead of three, as seen in its Red and Blue artwork.
142	Aerodactyl	Pokémon Stadium series Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Eyes are red instead of green, as seen in its Red and Blue artwork.
144	Articuno	Pokémon Stadium series Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Eyes are red instead of brown, as seen in its Generation I artwork. In the Pokémon Stadium series, it also has a blue beak and feet, as seen in its Red and Green artwork.
201	Unown H	Pokémon Stadium 2 Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Originally was asymmetrical in design.

Model discrepancies due to artist error

No.		Game(s)	Reason
125	Electabuzz	Pokémon Stadium series	Has six fingers on each hand.
168	Ariados (Shiny)	Pokémon Battle Revolution	Completely lacks a Shiny coloration.
191	Sunkern	Pokémon Stadium 2 Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Has green irises.
201	Unown (Shiny)	Pokémon Stadium 2	Completely lacks a Shiny coloration.
207	Gligar	Pokémon Stadium 2 Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Claws are white instead of pink.
208	Steelix	Pokémon Colosseum Pokémon XD: Gale of Darkness Pokémon Battle Revolution	Eyes are blue instead of red.
431	Glameow	Generation VI core series	Ears are at an incorrect angle. This is notably the only model changed between Generations VI and VII.