From Bulbapedia, the community-driven Pokémon encyclopedia.
Glitches are anomalies in software programs, including video games. They can cause various problems ranging from the purely graphical to completely wiping entire chunks of saved data.
They are usually caused by problems with a game's code, or from a player doing things the programmers did not anticipate, therefore causing the game to react unexpectedly. Below is a list of glitches in the Pokémon video games.
There are three glitches (the first two are only available in the Red, Blue and Yellow versions; the third one is available in the Gold/Silver and Emerald versions, and the Hall of Fame one is very minor) that do not necessarily always create glitched Pokémon, but are themselves glitches that cause events that would not normally happen in the gameplay.
- Glitch City: A glitch location consisting of mess of random map tiles that changes depending on the location where the player enters Glitch City. 
- Mew glitch: Allowing players to capture any Pokémon (most especially Mew) without modification, and allowing players to catch most of the glitched Pokémon. 
- Old man glitch: An in-game glitch which results in encountering a Missingno. or 'M, giving the player either 128 or 255 of the player's 6th item.
- Leveling past 100: If a Pokémon was caught at a level past 100, it could be leveled up with Rare Candies up until 255.
- Pokémon cloning: Variations of the Pokémon cloning trick exist in each Generation of the Pokémon games, each slightly different from one another. The most reliable version is in Generation III. This Pokémon cloning version allows players in the Emerald version to safely clone Pokémon, without any need for timing.
- Sprite glitch: Glitches that mess up sprites have occurred in all generations (mostly by cheating).
- Surf glitch: allows players to warp to places on the map where Darkrai and Shaymin lie. Note: This only works in some of the first Japanese versions to be released.
- Tweaking: This causes the game to fail to load the map and makes it appear black. Some cases have led the player to places such as Newmoon Island or Flower Paradise if the player goes the right way.
- Hall of Fame Glitch: When Missingno. has been seen on the save file, the player's Hall Of Fame is badly corrupted with entirely different Pokémon (players can even see Mew in the Hall Of Fame, whether they've seen Mew or not) and very glitched characters and names.
- Man on roof of Cinnabar Gym: If one does not have the key to the Cinnabar Gym, and surfs on the east coast and returns to land directly in front of the gym, a man will appear on the roof of the gym. A similar effect happens if the player walks into the Vermilion City Gym, walks directly left and then up so that they are facing the bottom-left trash can and press A to inspect it, or if the player is in the gatehouse to Cycling Road. One of the trainers in the gym will be misplaced and return to his usual spot once the text box disappears, and when in the gatehouse there may be a man standing on an object somewhere behind the guard.
- Prevented progress: If one evolves their starter Pokémon before they obtain their Pokédex from Prof. Oak, the game will assume that, since they have 2 Pokémon registered as caught, that they already have a Pokédex, and will not allow them to proceed. This glitch is only present in the Japanese Red and Green Versions.
- Invisible PC: There is a hotel in Celadon City that resembles a Pokémon Center on the inside. In the top-right space of the area that the player can walk on, there is an invisible, usable PC.
- Fishing in Statues: The player can use a Fishing Rod when facing the right or left of a gym statue. It will always say "Looks like there's nothing in here...", except in Misty's gym, where all the Pokémon obtainable in the gym can be caught.
- Q Glitch: A glitch enabled by the Pokémon Q (and Charizard 'M) which allows Pokémon stored in the PC to swap moves and stats.
- ZZAZZ glitch: A bizarre side effect of the Mew glitch using a Pokémon with a special stat of 251, 252, 254 or 255. When this is done, a Glitch trainer will appear. In the Red and Blue versions, after battling the Glitch trainer, numerous abnormalities will occur, including the player's name being turned into "ZZAZZ" and 3 of the player's Pokémon being turned into Bulbasaur, which oftentimes have learned one or more instances of the move Explosion. It has been known to erase a player's saved game. The abnormalities which occur in the Red/Blue version are not the same as those which occur in the Yellow version.
- Cut glitch: If the player cuts down a tree, stands on the spot, saves, turns the game off, then loads it, the player will be standing on a tree.
- Quick Level 100 Pokémon (Yellow only): This glitch is similar to the Mew glitch, but can be done in the Viridian Forest. First the player must go to the 2nd to last trainer and be out of his view (and must also not be able to see him). Walk one space and come into his view. Press start and use an escape rope to go to the Pewter City Pokémon Center. A, B, Start, and Select will not work. Now go try to go out of Pewter City towards Mt. Moon. The guy will stop the player and show him or her to Brock's Gym. Now the player must go to the small patch of grass south of Pewter City and North of Viridian Forest. Encounter a Pokémon and use Growl on it 6 times. (Try again and Growl less if the player gets a level 0 Pokémon at the end, instead of 1.) Now walk into the forest (the message 'Do you have a Pikachu?' will appear). The player will immediately go into a Pokémon battle with a level 1 Pokémon. When the player weakens the Pokémon, he/she must catch it. If the player uses it in a Pokémon Battle and it levels up it should skip straight to level 100 (as long as that Pokémon is one of any fully-evolved Pokémon or Mew, as the algorithm for the experience to the next level for those Pokémon is glitched and takes the experience to level 2 as a rather large negative number (which displays as a large positive number.) Note: The player can obtain different level 1 Pokémon by facing different Pokémon to the patch of grass south of Pewter City and North of Viridian Forest.
- Stuck in Wall: If the player lures an NPC into the grass above Pallet Town, she will block the player from following Professor Oak correctly, causing the player to become stuck in the wall of Oak's laboratory.
- 0 ERROR: Another glitch similar to the Mew glitch that causes Route 6 to become glitched.
Error codes (R/B/Y)
In Pokémon Red and Blue, there are several error codes that appear when the game is not functioning correctly. Problems such as these often crop up when the game's memory access is corrupted or when experimenting with glitches such as the Mew glitch. Usually, when an error code appears, the game does not freeze and the player is allowed to continue playing the game without resetting. There are thirteen known error codes in Pokémon Red and Blue:
|| Reason for error
|| Text Error
|| The text that is currently in the text box is wrong and should normally be in a different place. Sometimes displaying strange characters or Missingo like symbols
|| Event Error
|| Unable to complete an event (talking to someone, etc). This error is also known to exist in normal gameplay if the player has a broken or damaged cartridge. Can be seen in Yellow when finishing the game with 152 entries in the Pokédex.
|| Text Error
|| Happens when talking to signs or Televisions.Sometimes encountering missingo in some instances before displaying a 'Epic Fail' Screen.
|| Position Error
|| The current position of the player character is unrecognized.
|| Text Error
|| Unable to display correct/required text.
|| Pokémon Error
|| A Pokémon in the player's party is unrecognized. Most glitch Pokémon cause this error.
|| Sound Error
|| The sound clip that is playing is unrecognized.Mostly plays random pokémon sounds for no reason
|| Battle Error
|| Probably the easiest to find glitch of them all. Happens in a lot of situations, but only inside battles. Can be found in Pokemon Red and Blu, if the player fights a pokemon which should only be in the opposite game.
|| Graphics Error
|| When this error occurs, the screen turns white and the words "48 ERROR" pop up before quickly reverting back to whatever the player was previously doing. This error can be caused by the glitch Pokémon a. Some errors are followed by this
|| Text Error
|| Unable to display correct/required text.
|| Position Error
|| This error is similar to a 5 Error, but also generates random text such as "This is my graThe trainer blocked the ball! I2 59 ERROR"
|| Connection Error
|| This error occurs when data transferred between two cartridges via link cable is damaged, corrupted, or otherwise glitched.
|| Connection Error
|| This error occurs when data transferred between the Game Boy Tower and the Game Boy game is damaged, corrupted, or otherwise glitched by the Transfer Pak.
|| Text Error
|| This error is similar to a 0 Error, except the game doesn't explain that it is an error and instead the game freezes.
|| Event Error
|| This error confuses battle events with regular events, usullay leading the player into a fight with a compltely random and broken glitch Pokémon, or freezes the player's game.
|| Death Error
|| When the player gets this error, their game is dead. It cannot recover, and they'll be lucky if it can even be booted up again.
However, usually when the game presents multiple errors, it mixes codes (eg: 08 might be an unrecognized symbol) . This means that there are altogether 99 official errors that can occur in Pokémon Red Pokémon Blue and Pokémon Yellow. However, it is unknown if more errors are in Pokémon Yellow than the others games, but it is certain that they are 99 official errors in Pokémon Red and Pokémon Blue.
Mixed errors usually generated when the game mixes three or more errors, and instead of using standard error codes, the game looks in other Hexadecimal text slots, but as nothing was programmed to be there it instead displays other data that is interpreted as text. This may crash or freeze the game. If the player receives a mixed error, it is is recommended that that player resets their console so that no data is lost.
9 9 9 9 40 Blackout error
One error has been known for wild battles, the 9 9 9 9 40 Error can occur when the player hacks the game using an emulator, the error sometimes displays a black glitchy screen with random lettering and symbols scattered around, with the error message in one line where the move was supposed to be, the word 'error' isnt visible but is when the black masking is removed as it is in negative to the background as found with tests, the error is mostly in the emulator versions but is availible in the cartridge versions.
- Glitch dimension: Turns everything into strange, random colors and slows the ability to see the party screen and changes the "Poké" in PokéGear to random symbols. It is usually activated by first using the Coin Case and then speaking to the Machop at Vermilion City.
- Dratini glitch: After the player speaks to the Dratini in Blackthorn City and uses the Coin Case, the Coin Case's display will change what the coin case says from "Coins: ..." to "Which move?he pp of" permanently unless the game is turned off without saving.
- Celebi Egg Trick: Allows players to hatch as many Celebi as one desires using a number of steps.
- Shiny Ditto Exploit: By trading any shiny Pokémon to a Generation I game, having a wild Ditto transform into that Pokémon, then catching and trading the Ditto into a Generation II game, the Ditto will be shiny.
- Cut glitch: If the player cuts down a tree, stands on the spot, saves, turns off the power, and loads the game, the player will be standing on top of a tree.
Error codes (G/S/C)
Pokémon Gold, Silver, and Crystal feature a more detailed method of handling errors compared to Red, Blue and Yellow, although error messages are very uncommon in-game without the use of a cheating device.
| 'Object Event'
|| Text/Window error
|| This text appears when the player attempts to talk to a character who is supposed to start a cutscene e.g. Lance in the Hall of Fame room through the use of a location code. 
| 'No windows avail-able for popping.'
|| Text/Window error.
|| This text appears when an event attempts to bring up a message window yet the specified text/function is undefined - notably appears when HM06 is used outside of the TM/HM pocket 
| 'The window save area was exceeded.'
|| Text/Window error
|| It is currently unknown when this may appear. A possible error regarding text which exceeds the number of letters allowed (this may appear in some glitch dialog?) 
| 'Corrupted Event!'
|| Function error.
|| It is currently unknown when this may appear. A possible error regarding an event which has invalid data (This may appear in some of the more unstable glitches?) 
| 'BG Event'
|| Text/Window/Sprite error
|| It is currently unknown when this may appear. A possible error when attempting to force an event which changes the background to display text (May appear with a particular code to change a location's information?) 
- Hill glitch: East of Mauville City there is an Aroma Lady that will battle the player. If the player stands right behind the hill in her line of sight, she will see the player and walk onto the hill and stay there until the player leaves the area. This does not happen in Emerald due to her being a part of a double battle in the same area.
- Berry glitch: Freezes the growth of any berries which have been planted but not harvested, often occurs after the game has been owned for a year or played for over 100 hours, though not always.
- Thunderbolt glitch: The moves Thunderbolt and Thunder, when used in some Ruby and Sapphire cartridges, may cause the game to freeze or cause a sound effect to linger until the game is turned off.
- Pomeg glitch (Emerald Version only): A glitch that involves negative HP.
- Colosseum Master Ball glitch: Also known as the Infinite Ball Glitch; it is a glitch which involves switching the position of any Poké Ball on the same turn that it is selected to be used, so that the quantity does not decrease.
- Honey shop glitch: This is caused by the player using Sweet Scent or honey in a shop. When the player talks to the shopkeeper and selects "buy", he or she will see that there are no names or descriptions for any of the items in stock.
- Egg Nature Glitch: A well timed switch between boxes will allow the player to see the nature/ability/type of the Pokémon inside an egg.
- Acid rain: Rain, strong sunlight, hail and a sandstorm all occur on the battlefield when a Pokémon switching is knocked out with Pursuit during Hail or Sandstorm.
- Graphical Glitches: In areas such as the Great Marsh or the Ribbon Syndicate, standing in certain places may cause the foilage or the walls to bend and merge into other graphics near them. This is most likely because Pokémon Platinum runs on a 3D game engine.
- Black Belt Gibberish: For unknown reasons, a certain Black Belt in Sinnoh's Victory Road may speak glitchy gibberish upon defeat.
- Pal Park Glitch: Allows the player to migrate any number of Pokémon via the Pal Park, this is used to overcome the 6 Pokémon per 24 hours limit.
- GTS Glitch 1: In some copies of Platinum, the levels of a Pokémon might not be displayed on the GTS. In order to fix this, the player must contact Nintendo.
- GTS Glitch 2: In a Generation IV game, if the player deposits any Pokémon on the GTS that can evolve through trade (holding any necessary items), and then either waits for over 24 hours before taking it back, or trades for another Pokémon before taking the first back, it will evolve after being received.
- Main article: Glitch Pokémon
A glitch Pokémon is a Pokémon that exists in a game due to a programming or level design oversight or for beta testing, and as it was not intentionally placed inside the game by Nintendo or Game Freak, it might be hazardous to saved data. They were originally supposed to be placeholders for unused hexadecimal addresses in the game.
- Main article: List of glitch moves
A glitch move, is much like a regular move except the results are often undesirable. Like with glitch Pokémon, glitch moves were not programmed into the game on purpose and many have been proven to cause damage to game cartridges. The only widely known ones are those for Pokémon Red, Blue and Yellow. Many glitch moves are named after TMs or HMs (TM01 to TM55 and HM01 to HM05), but some have no name or a glitched, unreadable name. Some moves are of known glitch types (see list below), but most have either no type or an unknown type, and are often referred to collectively as "Super Glitch".
There are ways to teach glitch moves to certain Pokémon without usage of a cheat-code device such as GameShark, however, most of the time only glitch Pokémon will learn glitch attacks.
One way of teaching a Pokémon in Generation I a glitch move is trading to a Generation II game a Pokémon that will evolve by trading at a level when it will learn an attack in the next generation game, and then trading it back to the Generation I game. For example, trading a level 50 Haunter from Pokémon Red to Pokémon Gold will make the Haunter evolve into Gengar. Since it is level 50, it will learn Destiny Bond. If it is then traded back to Pokémon Red, it will still have the move, but the game won't recognize it properly since it is a Generation II move.
- Main article: List of glitch types
There are many different glitch types that are found to be the types of several glitch Pokémon. The majority of them are used for very few Pokémon; typically only one or two glitch Pokémon per type.
Aside from Glitch City in Generation I, there are several other areas which can only be reached by way of a glitch in the games. Examples of this are areas in the Sevii Islands that are retrievable via their index number pointer, however, do not have any other data. Sevii Isles 8 and 9 are the only index number areas which have actual map data. There are also other beta locations such as the Beta Safari Zone.
In the Generation II games, it is possible to get an item called the Teru-sama, the only description of which is a lone question mark. Generation III likewise has a mystery item. Both of these seem to have been placeholders just in case more slots for items were ever needed, something that came true with the Clear Bell in Crystal and the various newer items introduced just in FireRed, LeafGreen and Emerald, which register as the Teru-sama and mystery item if they are somehow moved into Gold and Silver or Ruby and Sapphire. There is also the Seal Bag, a glitch item obtained from the Generation IV GTS glitch.
The Teru-sama is a glitch item, but can be transformed into the GS Ball if it is given to Kurt in Azalea Town to capture Celebi in Ilex Forest. This works in the Japanese, English and European versions of Pokémon Crystal.
- Main article: Glitch Trainer
Glitch Trainers have been known to occur in the Red/Blue/Yellow versions. They are usually found if the player's name contains mostly special characters. There are also several special stat numbers used in the Mew glitch which cause glitch trainers to appear. Glitch trainers frequently use Glitch Pokémon in battle.
- ↑ http://www.trsrockin.com/glitchcity.html
- ↑ http://www.trsrockin.com/mewtrick.html
*Indicates glitches which have been officially acknowledged