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Second type glitch

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The Second type glitch (not to be confused with the dual-type Pokémon glitch) is a glitch in Pokémon Red and Green and the Japanese Pokémon Blue. It allows the player to transform a Pokémon into another Pokémon equating to the index number of its second type. Without the need of additional glitches, the glitch can be used for obtaining a maximum of 15 unique Pokémon species. More Pokémon are available if the player uses a glitch Pokémon with an invalid second type. The glitch can be used with single-type Pokémon, because internally their "second type" is identical to their first type. It is notable for being one of the first unofficial methods of obtaining Mew in the Generation I, through the use of a pure Water-type Pokémon, most commonly Magikarp. The glitch predates more popular glitches for obtaining Mew, such as the Mew glitch. The glitch is exploitable through two known methods.

This glitch is part of a division of popular Japanese version exclusive glitches known as select button glitches (Japanese: セレクトバグ select bugs), which exploit an oversight with the player's ability to move items using the select button. If the player registers an item using the select button and closes the menu, the position of the select button remains registered. Using this oversight, the player is able to swap invalid Pokémon and moves in the place of other Pokémon by entering another menu without opening the menu via the start button. This is the cause of additional glitches from "swapping" values of the game's memory.

Effects

The Pokémon that the player receives as a result of this glitch becomes an unstable hybrid Pokémon with a glitchy nickname, with the recipient Pokémon as the original Pokémon, and the donor Pokémon as a Pokémon equating to the index number of the original Pokémon's second type. This means that the Pokémon cannot be traded to a main-series Generation II game. As such, taking the Pokémon into the Day-Care Center on Route 5 changes it back into the original Pokémon before the player exploited the glitch, although any changes to its nickname and moveset applied after the glitch will remain the same. "Stabilizing" the Pokémon back into its original species (i.e. the recipient) allows the player to obtain a Pokémon with an illegal moveset in a similar way to glitches such as the Pokémon merge glitch. However, the player can stabilize the Pokémon as if it was originally the donor through evolution in the same way that the recipient would, or through Pokémon Stadium 2.

The glitch has a negative side effect of enabling and disabling flags in the player's Pokédex data and corrupting the player's item pack. The effects on the Pokédex vary depending on the method used.

Available Pokémon through type

Below is a table of the available Pokémon depending on the index number of the original Pokémon's second type. Note that single-type Pokémon have an identical second-type internally.

Index number (dec) Index number (hex) Type Pokémon
000 00 Normal-type "A" (Japanese 'M (00))
001 01 Fighting-type Rhydon
002 02 Flying-type Kangaskhan
003 03 Poison-type Nidoran♂
004 04 Rock-type Clefairy
005 05 Ground-type Spearow
006 06 Bird-type Voltorb
007 07 Bug-type Nidoking
008 08 Ghost-type Slowbro
020 14 Fire-type Arcanine
021 15 Water-type Mew
022 16 Grass-type Gyarados
023 17 Electric-type Shellder
024 18 Psychic-type Tentacool
025 19 Ice-type Gastly
026 1A Dragon-type Scyther
033 21 ヌ゙る* Growlithe

Method

Through the 13th item

The first discovered method of the glitch involves pressing the select button on the thirteenth item, exiting the menu using B,B and then swapping the thirteenth option with the first Pokémon by using the A button. This is possible either through the use of the Pokémon menu in battle, or the Day-Care Center on Route 5. Coincidentally, one of the altered Pokémon flags forces the player to 'see' Pokémon No. 152. A 152nd entry is possible in the Pokédex due to the fact that there are 19 "seen" and "own" Pokédex flags, and a unique Pokémon is stored for every bit. Due to technical limitations, this means that the game must store a minimum of 152 (19*8) Pokémon. In the Japanese versions, this appears as Missingno. (けつばん) but it appears as either Scyther or Farfetch'd in the English localizations. The reason for this is unknown.

By ginothepro
Videos are currently unavailable on Bulbapedia; instead, you can watch the video on YouTube here.

Through the 14th item

An alternative method changes different Pokédex flags, but does not activate a 152nd entry in the Pokédex. The player must first press the select button on the fourteenth item, exit the menu using B,B and then swap the fourteenth option with the first Pokémon by using the A button through the Day-Care Center. The Pokémon will then turn into an "A" (the Japanese version of 'M (00)) with a glitchy nickname. The player should then ask to receive the "A" from the Day-Care Center, and it will have "grown" to level 1. It should appear in the player's party as the second Pokémon. After swapping the fourteenth item with the first Pokémon through the Day-Care Center again, the player will this time receive a Pokémon depending on the second type of the original Pokémon before exploiting the glitch, while keeping the level 1 "A".

By ChickasaurusGL
Videos are currently unavailable on Bulbapedia; instead, you can watch the video on YouTube here.


Main
Multiple
generations
:
Cloning glitchesGlitch PokémonGlitch types
Generation I: --0 ERRORCut glitchCable Club escape glitchDokokashira door glitch
Error codesExperience underflow glitchGlitch CityGlitch dimension
Glitch movesGlitch TrainersItem duplication glitchJohto guard glitch
Mew glitchOld man glitchPewter Gym skip glitchPokémon merge glitch
Second type glitchRhydon glitchSuper GlitchZZAZZ glitch
Generation II: Celebi Egg glitchCoin Case glitchesError codesExperience underflow glitchGlitch Egg
Johto guard glitchSketch glitchTeru-samaTrainer House glitchGlitch dimension
Generation III: Berry glitchDive glitchPomeg glitch
Generation IV: Acid rainGlobal Terminal glitchesMimic glitch
Pomeg glitchRage glitchSurf glitchTweaking
Generation V: Sky Drop glitchFrozen Zoroark glitch
Generation VI: Lumiose City save glitch
Glitch effects: Game freezeGlitch battleGlitch song
Gens I/II only: Japanese text in English games
Gen I only: Glitch screenTMTRAINER effect
Gen II only: Glitch dimension
Lists: Glitch movesGlitch types
Glitch Pokémon (Gen IGen IIGen IIIGen IVGen VGen VI)
Glitches (Gen IGen IIGen IIIGen IVGen VGen VISpin-off)

Project GlitchDex logo.png This glitch Pokémon article is part of Project GlitchDex, a Bulbapedia project that aims to write comprehensive articles on glitches in the Pokémon games.