List of glitches in Generation I

This is a list of glitches that occur in the Generation I core series Pokémon games. It applies to both the original Game Boy and the 3DS Virtual Console releases unless otherwise noted.

Evolutionary stone bypassing
can be evolved without the use of an evolutionary stone after a battle. If the Pokémon has leveled up during the battle, and the battle has been finished with another Pokémon species whose index number corresponds to the index number of the evolutionary stone that causes the Evolution, the game will erroneously begin the Evolution as if the Pokémon evolved after leveling up.

Some glitch Pokémon with unusual evolutionary flags may evolve this way according to the game 'after exposure to an item', which is not necessarily an evolutionary stone.

Freezing the game in Oak's Laboratory
If the player holds "A" at the moment they interact with the Poké Ball in Oak's Laboratory, the game will be frozen until the player lets go of the button.

Indoors fishing oversight
In Cerulean Gym, the water tiles have wild Pokémon data programmed in, which allows players to fish. In, the and  work, but the  doesn't. The bug then returned in  but it was fixed once more in.

Lorelei's room in Indigo Plateau also has this issue, which was fixed in Yellow as well.

Invisible PC access
Celadon Hotel is based on the layout design of a Pokémon Center. In this map, if the player stands in front of where the PC would be in a Pokémon Center, the player can access an invisible PC.

There are also invisible PCs in the same position (accessible by facing up with the coordinates x=13, y=4 xblock=1, yblock=0) in Safari Zone rest houses 2, 3 and 4 (maps 223-225), but these positions are not normally accessible, so memory hacking must be done or Arbitrary code execution written using the 8F item can allow these extra PCs to be accessible without cheating.

All known invisible PCs do not exist in.

Extra invisible PCs:

Lift Key overworld misplacement
In the Rocket Hideout, if the player is standing to the left of the who has the Lift Key and talks to him, the Lift Key will appear underneath the player when he drops it. The player can still move around and collect it if he moves downward.

This glitch was fixed in, due to the Grunt automatically dropping the Lift Key as soon as he is defeated.

Lift goes to the same floor
In any lift of Pokémon Red/Blue/Green and Yellow, if the player chooses go to the floor they're already on, the lift acts like it is moving.

New-game Nidorino cry oversight
During the new game tutorial, the game shows 's sprite but plays 's cry.

Oak Poké Ball delivery text overlapping
If the player has no new registered as caught in the Pokédex (by only having the starter Pokémon) and/or no Poké Balls in his Bag (this includes buying/finding/obtaining any and then selling/tossing/depositing them) after defeating the  on,  will give five Poké Balls to the player after being talked to. During this event in the English versions, one of the lines of his dialogue appears over the previous line, instead of on a new one.

This glitch occurs in all localizations of and in the European localizations of. In the Italian Pokémon Red and Blue, there's also a word in this dialogue that overlaps the right border of the text box. In English Pokémon Yellow, it was fixed but the dialogue contains a typo instead.

Overworld sprite misplacement
If the player does not have the to the Cinnabar Gym, and s 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 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 gate to. 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 gate there may be a man standing on an object somewhere behind the guard.

Both of these variations of this glitch were fixed in some European releases of, such as the Spanish version, and in all releases of.

Walking with only fainted Pokémon
If the player has some fainted Pokémon and some that can fight, they can deposit all but the fainted Pokémon. After three steps, the player will black out. However, if two steps are taken, then the game is saved and reset, it resets the step count. If the player enters a battle with no Pokémon, the battle will start normally, but instead of sending out any Pokémon, the player immediately gets the black-out message. In, only one step is needed for the game to black out so this glitch does not work.

Instant Text trick
If the player goes into the Cerulean City Bike Shop without a bike voucher and cancels out exiting the shopping menu of the bike shop, the game never resets a text based flag. Instead of the game showing all the text character by character, it will instead now show all text on screen instantly. Going back to the shop later and buying the bike will reset the flag.

Binding move wrong side fainting glitch
This glitch was introduced in the later revision (v1.1) of Red and Green and seemingly does not occur in the v1.0 release. It was fixed in the English Red and Blue.

When the player's Pokémon is immobile due to being trapped by the opponent's, but the opponent faints due to or , then the player's Pokémon will faint in addition to the opponent's Pokémon. This does not occur if the player's Pokémon is the one using the binding move. Despite the player's Pokémon fainting, it will still have full health on the Pokémon menu.

In a link battle, because the Pokémon is only considered to faint on its Trainer's side of the link and not its opponent's side, it can cause a communication error.

Broken hidden items
In, there are six hidden items that do not function correctly. These hidden items are believed to have been fixed in Japanese Pokémon Blue and later versions (including the localized versions of the Generation I games).

Picking up one of these six specific hidden items causes the other five hidden items to disappear. If the player hands over a Fossil to the scientist in Cinnabar Island's Pokémon Lab (even if they choose not the revive it), all six hidden items reappear.

The broken hidden items cannot be detected by the Itemfinder. Instead, five of these six items have another set of coordinates that the Itemfinder believes them to be located at instead, although there is no item hidden at that position.

Japanese Red, Green, and Blue
NOTE: The following glitches affect all Game Boy versions of (1.0 and 1.1) unless noted otherwise.

Empty Pokémon List
If the player withdraws the from the PC at the very start of their adventure (meaning before they receive their starter Pokémon) and then attempts using it, an empty Pokémon List will appear and the Potion can be used, albeit to no effect. This was fixed for international releases and Pokémon Yellow, which will state "You don't have any/a POKéMON!" (Japanese: ポケモンが　1ぴきも　いない！).

Full Box glitch
If the player has six Pokémon in their party and all full Pokémon Storage System Boxes before watching the 's catching demonstration, the game will state that the box is full when the old man tries to capture the. The game will try to use the Poké Ball again infinitely afterwards, and every attempt results in this message causing an infinite loop. This forces the player to either reset the game or turn the power off. This is because the game thinks that the player is catching a Pokémon, even though it's actually the old man, the game produces a "temporary" Pokémon to hold, and if the catching demonstration ends, that caught Pokémon is deleted.

This glitch was fixed in the Japanese version of and in the localizations.

Pokédex glitch
In all Japanese Generation I games, if the player evolves their starter Pokémon before bringing Oak his parcel, Oak will assume the player already has the Pokédex and will offer to rate it instead of accepting the parcel. This prevents progression in the game, as the will not move until the player delivers Oak's parcel.

Silph Co. elevator entry swapping
It is possible to swap the positions of the elevator destinations in Silph Co. with the SELECT button as if they were items. Doing this in certain ways can change the list type in at least one way (i.e. to a list of 'boxed Pokémon') and corrupt data.

This glitch works in the Japanese but the effects differ from.

Swift effect glitch
Swift was designed to never miss, but due to a programming error in Pokémon Red, Green and Blue (as well as all known revisions of Japanese Yellow), the move is capable of missing under certain circumstances (i.e. if the foe has raised evasion, or is under the invulnerable stage of or  or possibly from 1/256 miss chance that affects other 100% accuracy moves) unless the foe has put up a.

This was amended in the English versions, which have Swift never miss (including when a Pokémon is under the invulnerable stage of Fly or Dig) regardless of whether the foe has set up a Substitute or not.

Whirlwind text box overflow
In these games, if a Pokémon uses on a Pokémon with 5 characters in its name, the exclamation mark character overlaps with the border of the text box. This was corrected in the Japanese version of with the addition of a line break.

Yellow
NOTE: The following glitches affect all Game Boy versions of Japanese (1.0 to 1.3) unless noted otherwise.

Delayed Pikachu follow
In Pokémon Tower, if the player steps on the purified zone with a fainted Pikachu, and quickly pushes (B) and takes two steps, Pikachu will not match the player's first step until the player takes their second step and will continue to follow at a delay. As a result, Pikachu may end up a space distant from the player or overlapped with them. Walking back onto the purified zone while overlapped will return Pikachu's position to normal, regardless of speed.

Thanks to the Pikachu off-screen glitch, it can be done everywhere.

Freezing Pikachu
If the player jumps off a cliff when Pikachu is dancing, the Pikachu's sprite will be frozen for 7-8 seconds.

NPC over the grass
In the Viridian Forest, there is a Lass whose sprite is clearly over the grass. This trainer won't move because she doesn't have a range at which she will walk up to the player, so she has to be battled by walking up and talking to her.

Friendship item effect
This causes a no-effect item to still increase 's friendship value, such as using a at full.

This glitch was fixed in Generation II.

Pikachu off-screen glitches
With the use of in-game event that causes a walking Pikachu to stay (Pikachu being put to sleep by in Pewter City's Pokémon Center, Pikachu meeting Bill at, Pikachu falling in love with  at the Pokémon Fan Club) one can bring the walking Pikachu off the screen and cause memory corruption glitches such as a forced Glitch City and causing NPCs to turn when they shouldn't.

For each step Pikachu is off the screen, a memory address is corrupted from D437 and onward, and the values depend on where the player steps, with south being 01, north being 02, west being 03 and east being 04. Through this, the player can make Pikachu's happiness one of these low values, cause a Glitch City and through specific movement, set the play time to 255:59.

In addition to use an in-game event that causes Pikachu to stay, Pikachu can also be forced off the screen with a certain Glitch City such as 's Safari Zone exit Glitch City, or specific glitch items, including the “Lg-” (hex:6E) and “Rival's” effect/“Jack” effect glitch items such as “E tE” (in Red/Blue) or “o” (in Yellow); hex:94.

With more advanced applications of the glitch, it is possible to max out Pikachu's happiness or cause it to do one of four special actions (winking, the fishing action, the confused action or the 'disapproval' action) when the player character talks to it. Arbitrary code execution is also possible by creating a specific glitch sign in the Pokémon Fan Club.

All glitch items are available with the item underflow glitch. Lg- is also available through pPkMnp' ' (Ditto glitch Special 194) converting a Super Rod when it is the fifth item.

Through an in-game event that causes a walking Pikachu to stay:

Through a Glitch City and glitch item:

Pikachu off-screen text box arbitrary code execution:

In all games
NOTE: The following glitches affect all Game Boy versions of (1.0 and 1.1) and of Japanese  (1.0 to 1.3) unless noted otherwise.

--
If a transforms into another Pokémon and then switches around the copied moves with the SELECT button, after the battle the Ditto will not have  and will instead have. This can also be done with other Pokémon by having them use on Transform, or use Transform directly, such as.

0 ERROR glitch
A glitch similar to the Mew glitch that causes to become glitched.

Battle draw theme oversight
Prior to Generation II, having the player character draw in a Pokémon battle causes the victory theme to play even though the player has lost.

Disabling NPCs animation
When the player walks, the screen moves the objects of the stage where you are, including NPCs. That movement alter the animations of the NPCs, disabling their animations.

Bide errors
The stored damage from can hit (but not always) a Pokémon under the invulnerable stage of  or. If Bide deals damage to a Pokémon under Fly or Dig, the game will reveal its sprite early. This also causes a small animation glitch with Dig where it appears that the enemy Pokémon rises from the ground off the top of the screen instead of the enemy rising up from 'underground'. There is no animation glitch with because the game has no animation on the opponent's side of Fly returning from the top of the screen to the ground—the game only reveals the sprite.

Catch rate errors
There are two minor bugs in the catch rate formula, both due to programming oversights.

The Great Ball is given an independent value of 8, compared to the values of the other Poké Balls being 12 when calculating Steps 5-7.

Due to an issue with Step 6, a Pokémon with 1 HP left has the same chance of being caught as the same Pokémon with ⅓ of its total HP remaining. If a Great Ball is used, then it has the same chance at any point with ½ of its remain HP or less, due to the oversight above.

Changing NPC sprites
When the walking through walls glitch is used and the player flies to Lavender Town, they can activate this glitch. They must walk down to and walk through the side of the gate rather than actually going into the gate. Once this has been done, every NPC will have the same sprite as the player. Encountering a wild Pokémon fixes the sprites. This is due to the fact that the game fails to load the sprite graphics properly.

Counter glitches
may strike back damage from an attack that isn't Normal- or Fighting-type. For this to happen, the Counter target must have not selected any move the turn Counter was used (for example, due to being frozen, asleep, or switching out), and must have moved first and used a Normal- or Fighting-type damaging move the previous turn. In addition, Counter may also strike back damage from one's own attack. This occurs if the Counter target previously used a Normal- or Fighting-type damaging move before the Counter user successfully used any damaging move during the same turn. If, in the next turn when Counter is used, the Counter target doesn't select a move, the Counter user's own damage will be dealt.

In Link Battles, Counter may also trigger desynchronization errors. This occurs due to the last move pointed by the cursor in the move selection menu being treated by the last move actually used if the Pokémon switches out. This oversight can also be exploited outside of link battles to make the opponent's Counter hit or miss at will under specific circumstances.

Critical hit ratio error
and Dire Hits are intended to quadruple the critical hit rate, but due to a glitch, they will quarter the chance of scoring a critical hit. This was fixed in.

Cut glitch
The Cut glitch can refer to two different glitches in Generation I involving the move.

Invisible tree
There is a tree near the bottom of. If this particular tree is cut down and then the player walks five steps west from where the tree was (so that the spot where the tree used to be is at the edge of the screen) and then walks back their path will be blocked as if a tree was still there. Even though the tree is not visible, it can still be cut down normally using the move.

Standing on a tree
If the player s down a tree, stands on the spot where the object was, saves, turns the game off, then loads it, the player will be standing on the tree. The same can happen with Pikachu in.

In Celadon Gym in Pokémon Yellow, Pikachu can also end up standing on a tree after certain battles.

This glitch occurs because the Generation I engine would not store the data needed to remember that the tree had been cleared.

Cycling Road access requirement bypassing
If the player does not have a Bicycle (or it has been deposited in the PC), it is still possible to reach by holding down the left button while the guard attempts to prevent the player from entering the Cycling Road. Upon entering Cycling Road, the player will be automatically riding a bike, despite not having one.

This is because pressing left on the d-pad actually overrides the "walk back to the right" movement, thus ignoring the return movement.

Defrost move forcing
If a Pokémon is defrosted before it would have moved that turn, it uses a move that turn, even though it couldn't select a move that turn due to being frozen. However, this move can differ between the games in a link battle, causing desynchronization. Additionally, this can also allow a Pokémon to use a move with no remaining, causing an underflow.

If a Pokémon is defrosted, in the game of the owner of the defrosted Pokémon, the move used will be the last move the player had the cursor over. Since the player does not get to select a move while frozen, this can be a move of another Pokémon in the party. The value that manages this is set to 0 at the start of a link battle, so if the player has never moved the cursor over a move during that battle, the used move will be the glitch move.

In the game of the other player, the move used will be the last move used by the defrosted Pokémon (reset upon switching), or the first listed move if it has not used a move since switching.

PP is deducted from the move the Pokémon uses in other player's game (even in its owner's game), regardless of its current PP. If the move had 0 PP, it underflows to 63 PP and removes the effect of one PP Up.

Ditto assumption
In Generation and, any Pokémon that uses  is regarded as a  in its new form; this means that if the player catches a  or a glitch Pokémon which has used the move Transform, or a Pokémon which has used Transform via , instead they will obtain a Ditto. Mew turning into Ditto was not an issue, because wild Mew could not have been legitimately encountered. This system was later changed in Generation III, where wild Mew could be encountered.

Ditto DV manipulation
If a wild Pokémon s again while it is already transformed, when it is caught it will have the DVs of the first Pokémon it transformed into. The caught Pokémon will always be due to the Ditto assumption glitch.

This can be abused to cause the Pokémon to have DVs that correspond to those of a Shiny Pokémon in Generation II or when converted by Poké Transporter. If a Shiny Pokémon from Generation II is taught, it can copy Transform with Mimic from a wild Ditto (before Ditto transforms) to facilitate this.

Division by 0
During damage calculation, the game will eventually attempt to divide by 0 in the following two cases. In both cases, this causes the game to freeze indefinitely (due to the algorithm looping infinitely).

The attacker's current Attack/Special stat is higher than 255 and the defender's current Defense/Special stat is lower than 4.

The defender's current Defense/Special stat is 512 or 513 and the defender has used /. In addition, if its current Defense/Special stat is 514 or higher when / is up, it will be treated as if it was much lower due to a roll-over glitch.

Dual-type damage misinformation
In Generation I, Pokémon with two types that have a weakness and resistance to the same type receive neutral damage from that type, but the incorrect message is displayed.

For example, moves do neutral damage to, but if Gyarados is hit by a Grass-type move, the game erroneously states that the attack is "not very effective...".

The game prioritizes on which message to display for each 'special' scenario (where normal damage is not dealt) based on each scenario's internal ordering. The higher the ordering determines what message the game will display. Grass against Water as 200% damage for instance is the 4th entry, whilst Grass against Flying as 50% damage is the 27th. Consequently, in this example, the game chooses the message for scenario #27, returning the wrong message "It's not very effective...".

This glitch does not occur in 🏴󠁧󠁢󠁥󠁮󠁧󠁿.

If an attack is super effective or not very effective against one type and does no damage against another type (for example, against ), the game will erroneously state that the attack missed.

Order of priority of messages
This list is presented in the reverse order to which they are stored in the game data. Messages higher on the list take priority over those lower on the list.

Exp. All oversight
If the player has an Exp. All in their bag and uses two or more Pokémon from their party in battle, then the total amount of experience gained overall will be decreased depending on the number of Pokémon used.

Experience PC withdrawing glitch
In Generation I, attempting to withdraw a level 1 Pokémon using the "Medium Slow" growth algorithm will softlock the game. This also applies to Pokémon using the "Medium Fast" growth algorithm for Level 255, "Fast" for Level 255, and "Slow" for Level 237.

Certain glitch Pokémon use invalid growth algorithms and have the game freeze when they are withdrawn at specific levels as well. For example, in, 'M (00) uses an invalid experience curve 26 and the game will freeze if the player attempts to withdraw a level 0 'M (00). Level 0 'M can be found with the old man glitch if the player does not pick a preset name.

Additionally, if a Pokémon in the "Medium-Slow" growth algorithm is withdrawn between Levels 245 to 255, it will become a Pokémon with a level between 59 and 125, depending on the exact Level of the Pokémon deposited. A Pokémon in the "Medium-Slow" growth algorithm that is withdrawn between 238 and 255 will become a Pokémon with a level between 39 and 146. A Pokémon withdrawn in this manner will have its stats recalculated, which may lead to it having more HP than its maximum HP.

Experience underflow
In Generations I and II, level 1 Pokémon using the "Medium Slow" growth algorithm will jump from level 1 to level 100 after gaining a of experience points.

Gate access restriction
Certain gates which can be accessed after the player passes Cycling Road will have guards that restrict the player from passing if the Bicycle is deposited in the PC, even though the player does not require a Bicycle.

Ghost identity unveiling
When encountering a in Pokémon Tower without having a Silph Scope, it is possible to see its true identity by viewing the stats of any Pokémon in the player's party. However, this glitch is only graphical, and it is still impossible to fight or catch it.

Ghost Marowak bypassing
Using a Poké Doll on the in Pokémon Tower with or without the Silph Scope will cause it to permanently disappear.

Hall of Fame corruption


When glitch Pokémon have been seen on the save file, the player's Hall of Fame is badly corrupted with entirely different Pokémon, even glitch Pokémon, and very glitched characters, names and levels. This does not affect the Pokémon themselves, rather the data seen in the Hall of Fame, and is caused by the contents of the sprite decompression buffer that is stored in SRAM overflowing into memory allocated for save data when a glitch Pokémon's sprite is decompressed.

Haze opponent crippling
If is used to thaw a frozen Pokémon when it still needs to recharge from, the Pokémon will thaw out but it will be unable to make a move until it faints even if a Fire type move is used later. This glitch was fixed in Pokémon Stadium.

It is similar to the Sky Drop glitch in Generation V, because both glitches permanently make the opponent unable to move until it faints or is switched out (although switching out the Pokémon is normally not possible).

HP recovery move failure
If a Pokémon uses a recovery move (, or ) and the difference between its current HP and maximum HP is 255 or 511 (or any number that leaves a remainder of 255 when divided by 256), the move will fail the same way it would when the difference is 0. This glitch does not occur in Pokémon Stadium.

This is caused by the comparison that checks whether the current HP matches the maximum HP erroneously not correctly incorporating the upper byte of the HP values.

Hyper Beam + Sleep move glitch
If a Pokémon that has just used and has yet to recharge is targeted with a sleep inducing move, any other status it may already have (,, , or ) will be ignored and sleep will be induced regardless. In addition, the sleep inducing move will never miss, as it will skip any accuracy checks in a similar way to.

Furthermore, if the Pokémon was badly poisoned (by ), the Toxic counter will not be reset.

Index #000 post-capture
In Generation I, if the player manages to capture an 'M (00) or 3TrainerPoké $ an invisible wild will still be in battle with the player where 'M (00) was before, and the battle will not end. This Ditto can then be caught.

Invisible Prof. Oak
If the player attempts to leave too many times when choosing their first Pokémon then the player, Prof. Oak and the middle Poké Ball's sprites will vanish. Pressing start will pull up some glitched text on the screen, but exiting the start menu will fix everything.

Invulnerability glitch
In Generation I, if a Pokémon is fully or hurts itself in  while in the semi-invulnerable stage of  or, all moves (with the exception of ,  and possibly the unleashed damage from ) from the opponent will miss or fail until the user switches Pokémon, finishes the battle or successfully performs a  (specifically, Fly, Dig, , , and ). The user's Pokémon can attack normally during this glitch.

This glitch was fixed in.

Landing on an NPC
If the player lures (by blocking their movement in certain directions) an NPC below a ledge that can be jumped over, it is possible to land on top of the NPC when they jump over the ledge.

Level-up learnset skipping
Pokémon cannot learn moves they should learn at a level if they earn enough experience at once to skip that level.

For example, if a level 4 earned enough experience points for defeating a single Pokémon to reach level 6, it will not learn, a move it would normally learn at level 5.

Leveling past 100
In Generation I and II, if a Pokémon is obtained at a level above 100, it can be leveled up with Rare Candies up to level 255. If a Rare Candy is fed to a level 255 Pokémon, its level will be reset to 0 due to an overflow in a single byte. If a Pokémon above level 100 levels up due to experience, its level will be reset to 100.

Menu glitch
If the player holds A when the game is saving, the menu won't disappear until player stops holding A.

Mirror Move glitch
During a Link Battle, if and a  (such as  or ) are used together, the two player's games may become desynchronized due to one game interpreting that the attack used was Mirror Move (and failing) and the other game interpreting that the binding move was used instead.

Pallet Town NPC misplacement
If the player stands outside of Professor Oak's Lab in Pallet Town, the person outside it will eventually stand on the Lab's door. This is because the door tile was programmed as a non-solid tile.

Perpetual spinning animation
If the player saves the game having just entered the Safari Zone and leaves, the game assumes that the player is just entering the Safari Zone entrance, as it does not save that the player is currently in a paid Safari Zone session. Thus, upon passing by the desk, the player is prompted to pay for another Safari Zone session, although they are now traveling out towards the town below. Because the player is supposedly in a Safari Zone session, the game counts down steps passively. Upon exiting towards the bottom into Fuchsia City, the player must Fly to Viridian City and enter Giovanni's Gym. Inside, the player must walk along the spinners, proceeding to be spun around. After taking enough steps to deplete the (invisible) counter, the player freezes, the PA "ding-dong" noise will sound, and a message will pop up saying that the player's Safari Zone session is now over. If the player is in the middle of a spin while this happens, the player will be transported to the Safari Zone entrance as if they had just left the Safari Zone, and upon moving will perform the spin animation, and move slower. The player has full control over the movement of the character; the only difference is that instead of the walking animation, the spinning animation is played.

Poison/Burn animation with 0 HP
If a poisoned/burned Pokémon with low HP is confused and in the next turn loses its HP, the HP will be 0, but before it faints, the message and the animation of the poison/burn will appear, although the Pokémon doesn't have any HP. This also happen with a move which reduces the user's HP, like Take Down. This was fixed in Pokémon Gold/Silver.

Pokémon Storage System healthy party deposit
It is possible for the player to deposit all Pokémon except fainted ones and a black out will occur but only after four steps in the same session. In it is possible to progress further by saving the game before traveling four steps to reset the 'remaining step count' to 4 when the game is reset, though this is no longer the case in  because the remaining step count was changed to default to 1 step. The player immediately has a black out if entering a battle with just fainted Pokémon.

Prevented progress
If the player has at least two registered as caught in the Pokédex before obtaining it from  (either multiple non-related species or an evolved form of the starter Pokémon), the game will assume that they already have the Pokédex, and will not allow them to proceed.

This glitch affects all versions of the Japanese (1.0 and 1.1),, and  (1.0 to 1.3). The glitch is fixed in the international releases of, but remained in the international releases of.

In the Japanese Pokémon Yellow, it is also possible to perform this glitch by exploiting the save corruption glitch.

Psywave desynchronization
If a Pokémon uses in a link battle, there is a small chance the games will generate a different number of pseudo-random numbers, causing desynchronization.

When a Pokémon uses Psywave, a random number is generated between 0 and 255. If the player uses Psywave, if the generated number is greater than or equal to 1.5× the Pokémon's level (rounded down) or it is 0, the number is discarded and a new number generated; if the opponent uses Psywave, if the generated number is greater than or equal to the Pokémon's level, the number is discarded and a new number generated. As such, if the generated number is 0, the Psywave user's game will generate a new number, whereas the non-Psywave user's game will not. This causes all subsequent pseudo-random numbers to be desynchronized.

Psywave infinite loop
If a level 0, 1 or 171 Pokémon uses, the game will continuously generate pseudo-random numbers, hanging indefinitely. However, this is not an issue in normal gameplay, as Pokémon can only be obtained at these levels via glitches.

When a Pokémon uses Psywave, a random number is generated between 0 and 255. If the generated number is greater than or equal to 1.5× the Pokémon's level (rounded down) or it is 0, the number is discarded and a new number generated. As such, there is no number that can be generated for a level 0 or level 1 Pokémon that will not result in the result being discarded and a new number being generated.

If a level 171 Pokémon uses Psywave, the upper bound would be 256; however, since this value is stored in a single byte, it overflows to 0, causing the same issue as a level 0 Pokémon.

Red Bar Glitch
If a Pokémon is in a critical health status, the game will start to play a sound to let the player know their Pokémon is low on health and about to possibly faint. This sound has an unintended side effect of causing other sounds and animations to not play. This glitch has become very well known and is used often in speedruns for the Generation I games.

Rematching Trainers
To perform this glitch, the player must have some Pokémon which can lose a battle easily, so they may wish to have one Pokémon, a ed Pokémon or both. They must be inside a cave, e.g. Mt. Moon or. They must, finally, have access to an unbattled Trainer who is in a cave. They must encounter a wild Pokémon while in a Trainer's eyeline. This wild Pokémon must proceed to defeat the player, sending them to a Pokémon Center. They then must re-enter the cave the Trainer is in. The Start menu will pop up. Upon closing it, the Trainer they escaped from will fight the player. However, if the player defeats them, this is not interpreted as beating the Trainer, and the player can challenge them again.

Save corruption
In, with no save file, when the player saves the game and turns off the power a little time after the Yes/No box disappears the player will have 255 Pokémon in the party the next time the file is loaded.

If the player turns the power off at the wrong time, the save file will either be corrupted or will appear normal. The right time to pull off the glitch is about twenty frames after the A button is pressed, but in Yellow it is about ten frames later.

The first few Pokémon are level 255 'M (FF) (Red/Blue) or Q_◣ (Yellow), with all of their stats as "F35" (65535), four TM55 as their moves with 63/0 PP and with a nickname and OT of many repeating "9"s. Pokémon past number six do not have all of these properties.

The data regarding Pokémon past the sixth position use other parts of the game's memory misinterpreted as Pokémon data, therefore swapping these Pokémon around or healing them can affect the game. If the player switches the first Pokémon with the tenth Pokémon, they will have 255 items. Switching the items past slot 20 will allow for more precise memory editing because there are only two pairs of memory addresses manipulated; displayed as an item and item quantity, while a "post-six" Pokémon uses many more bytes.

After performing the glitch, the poison effect will occur as the player walks around. In English versions, swapping the first-ninth Pokémon with the tenth will cause to player to have seen and owned 152 Pokémon in the Pokédex.

Using the following equation, it is possible to calculate what memory address any item, including invalid items is using, provided that the memory address is odd.

Memory address = [First item position address -1] + [Cursor position] + ([Cursor position -1])

The item address that follows an item is displayed as a quantity.

Beating the game quickly
As there are no memory protection measures in place in the Generation I and Generation II games, it is possible to use this glitch to do a number of things, such as beating the game in under five minutes. Below is one method of doing this that requires no luck manipulation:

In Pokémon Yellow, the memory address D364 is used for the last map location for walking through certain exits, including the exit for Red's house and the first item position address is D31D. This means that the correct cursor position can be expressed as:

D364 = D31C + [cursor position] + [cursor position -1]

This has no actual answer because D364 (54116) is even, so the address must be a quantity, but if D363 is used, the answer comes to hex: 24 (dec: 36). Therefore, the memory address D363 (current block of the player's X-position) corresponds to item position 36 (hex: 24) and the quantity of item 36 is the aforementioned warp location address. The cursor position in hexadecimal can be checked by highlighting an item in game and checking the memory address CC35.

As the index number of Pallet Town is 0, the player can access 255 locations by tossing the 36th item (as tossing one ×0 item causes an underflow to 255). The index number of the Hall of Fame room is 118, so the player must toss exactly 138 of item 36 to change the warp destination to the Hall of Fame. If the player stands on the right side of the exit mat item 36 should be a Master Ball, while if the player stands on the left side of the exit mat, it should be the hex:00 glitch item which would appear as some glitchy blocks with a multiplication sign in it.

In Japanese versions
The glitch works in Japanese Blue but the game has to be reset some time after the "!" mark appears in "(PLAYERNAME)はレポートに しっかり かきのこした!". In Japanese Yellow it is possible with the same procedure as English Red/Blue and Yellow, but in order to corrupt the number of items the player has to replace the ninth Pokémon instead of the tenth to avoid a freeze after closing the items pack.

Save reset oversight
This is a glitch that causes the player to always receive the "You can't get off here." message when trying to use the Bicycle even when they are not on the Bicycle. It also causes the "Cycling is fun! Forget <sc>Surf</sc>ing!" message to appear when trying to use (using the  "Surfboard" item doesn't cause this message to appear).

If the player's current save is on, or  (Cycling Road), the WRAM address D732 (D731 in ) is normally set to 21h (5th bit is on).

Normally when the player brings up the Continue/New Game/Option menu many of the variables from the current save are loaded so that the game works properly when the player selects the "Continue" option. Most of these variables are reset back to their default value if a new game is loaded but not the WRAM address D732 (possibly due to an oversight by the game developers).

This means starting a New Game with the current save on Cycling Road will cause the "You can't get off here." message to appear when trying to use the Bicycle from any location. The effects of this glitch are only visible once the player obtains the Bicycle or the Soul Badge and a Pokémon with.

The glitch can be fixed by performing any one of these actions:


 * Using, , , or an Escape Rope
 * Entering and leaving Cycling Road
 * Blacking out (both in battle and in the overworld)

It has been reported that this glitch may occur without starting a new save file when the current save is on Cycling Road, but the cause is unknown.

Another version of this glitch can (but not always) appear when performing the Fossil conversion glitch in the Japanese. Unlike the "New Game" version, entering and leaving Cycling Road doesn't fix the glitch.

Save Surf exploit
The glitch is performed by standing next to a water tile that is facing up, left, or right, walk in that direction and pressing start without letting go of the D-Pad. The game then needs to be saved and reset. When loading the saved data, the player will be facing in the direction that was being held down when the start button was pressed. Using will cause the player to surf on the tile immediately south, even if it is not a water tile.

When loading a save file, the player usually starts facing south. This is because of the limited data in the game. This glitch causes the player to face in a different direction, which confuses the game.

Since statues are treated as water tiles, this glitch can be performed by using a statue as the water tile. Most notably, this glitch can be used to bypass the sailor in order to re-board the S.S. Anne after it has set sail.

Silent Indigo Plateau
In the battle against at Indigo Plateau, if the player evolves a Pokémon in battle and defeats Blue, the music will be muted until Professor Oak comes to congratulate the player.

Sprite corruption
The sprite corruption glitch is a glitch that alters the appearance of the in Generation I, making the sprites appear to be cut into pieces or even unrecognizable in some instances.

In Generation I, many glitch Pokémon will distort battle sprites upon their encounter; however, this can be fixed by viewing the stats of a non-glitched Pokémon in the overworld. There are other methods to the glitch, some of which involve using a Pokémon Center to heal the player's Pokémon when in a glitched area, visiting Glitch City, or catching certain glitch Pokémon.

In other generations, it may occur when a cheating device is used.

Stat modification errors
Every time a Pokémon successfully uses a move that affects a stat stage (either raising for example with, or lowering it for example with ) of any of the two Pokémon in battle, the following happens:
 * The stat in question is recalculated from its out-of-battle stat and stat stage.
 * If the target was the player's Pokémon, badge boosts are applied to all of its stats (if the player has the corresponding badge), boosting them by 1/8.
 * If the Pokémon whose turn it is not is paralyzed, its current Speed stat gets quartered.
 * If the Pokémon whose turn it is not is burned, its current Attack stat gets halved.

This leads to three notable unintended stat-related effects:
 * Whenever one of the player's Pokémon's stat stages is modified, all of its other badge-boosted stats are multiplied by 1.125 again, even though they were already boosted. (The affected stat is recalculated correctly.) This effect can stack until a stat reaches the maximum of 999.
 * When a Pokémon is burned or paralyzed, the Attack/Speed drop from the status will be applied again whenever its opponent uses a move that modifies stat stages (either raising its own or lowering the enemy's). This will similarly stack until the stat in question has dropped to the minimum of 1.
 * When a burned or paralyzed Pokémon raises its Attack or Speed stat respectively with moves such as Swords Dance or Agility, the stat is recalculated in accordance with the boosted stat stage, but the status drop is not applied to it afterwards (since it's erroneously applied to the wrong Pokémon), effectively nullifying its effects.

All of these issues were fixed in the Pokémon Stadium series.

Statue water tile oversight
The player can use or a Fishing rod when facing the right or left of a Gym statue. The Old Rod continues to pull up, as it ignores location, but the Super Rod (and the Good Rod in Yellow) will display the message "Looks like there's nothing in here..." everywhere other than the Cerulean Gym, which has wild Pokémon normally.

Struggle bypassing
In Generation I, a Pokémon can avoid using by allowing the game to self-select a move to be used, which can happen to any move used immediately after a Pokémon is thawed out after being, or due to the effects of one of several moves (, , , , , , and ) because of the auto-selection involved with. A move used with 0 in this way  to the maximum possible value, 63 PP; due to the way the data is structured, if this occurs, a move on which 0 PP Ups had been used will gain full PP Up status, while a move on which PP Ups had been used loses one PP Up boost.

From Generation II onward, this bug is addressed by preventing a move from being executed if it has 0 PP.

Substitute HP drain bug
In Western, -draining moves are supposed to miss against a like in the Japanese versions, ,  but instead hit the substitute due to a programming oversight.

Substitute sprite vanishing
Using a sacrificial move like Explosion on a substitute and having the damage break the substitute prevents the user from fainting. The sprite of the user vanishes regardless.

Substitute + Confusion glitch
If a Pokémon with a Substitute up hurts itself due to confusion, or due to 's or 's side effect, damage will be dealt to the opponent's Substitute instead. If the opponent doesn't have a Substitute up no damage will be dealt to any Pokémon.

Substitute and Minimize glitch
If the enemy uses Substitute or Minimize and the player goes to view the stats of any Pokémon and then return to the battle, the sprites will be changed. The enemy will have the sprite of the Pokémon's player but broken, and the Pokémon of the player will have the Substitute or Minimize sprite. The sprite of the rival can change if the player goes to view the stats of any Pokémon in the team.

S.S. Anne reboarding
After the S.S. Anne leaves the dock for the first time, it's possible to make it reappear later. To perform this glitch, the player must stand one tile above and to the left of the sailor guarding the harbor, take a step right and hit the Start button at the same time, save and reboot. After verifying that the player is facing right and without moving, a Pokémon must be selected to, thus making the player surf on top of the sailor. Then, after walking down to the harbor, the boat can be entered.

With Leech Seed
If the target of Leech Seed is also under the effect of (or was under that effect and healed itself with ), because Leech Seed and Toxic both use the same damage algorithm, Leech Seed damage will be affected by Toxic's N parameter, and will increase each turn. This does not occur in Generation II onward.

With Rest
If a Pokémon by  uses, the Toxic counter will remain, with the N value not being reset. If a Pokémon is then poisoned, ed, or affected by Leech Seed, the damage will draw upon (and increment) the N value, and will increase each turn. This does not occur in 🏴󠁧󠁢󠁥󠁮󠁧󠁿 or Generation II onward.

Transform + Mirror Move/Metronome PP error
If or  is used by a ed Pokémon, the move of the same slot in that Pokémon's actual moveset will have its PP increased by 1. This occurs even if there is no move in that slot, which can prevent the use of or cause a softlock when targeted by. PP of slots without moves will not be reset to 0 when healing at a Pokémon Center; the glitch can only be repaired by repeating it 256 times, at which point the PP count will overflow to 0.

Trapping sleep glitch
To perform this glitch, player's Pokémon has to be by another Pokémon. Because it is bound, the player should use healing items until the binding ends. If the opposing Pokémon then puts player's Pokémon to sleep on the turn the binding ends, the player's Pokémon will never move. To fix the glitch, the player has to cure the sleep status.

Vending machine glitch
If the player has enough money to buy a Fresh Water (at least 200) but not enough to afford a Soda Pop or Lemonade, the vending machines atop Celadon Department Store still allow these more expensive drinks to be purchased. The player's money will be reduced to 0 rather than becoming a negative number.

Victory Road Bicycle music quirk
If, while riding the Bicycle in Victory Road, the player falls through a hole, they will, on landing, no longer be riding the Bicycle; nonetheless, the Bicycle theme music will continue to play until the player enters a battle, leaves the dungeon, changes floors, or resets the game.

This glitch occurs neither in the Japanese nor the international versions of Pokémon Yellow; instead, the Bicycle music does not play at all in Victory Road.

Walking through an NPC
If the player lures an NPC onto the path that Professor Oak takes to bring the player to the laboratory, Professor Oak and the player will walk right over and through her.

Walking through walls
To walk through walls, the player must trick the game into letting them exit the Safari Zone while it still thinks the Safari Game is running, then jump off a ledge exactly when the game thinks the Safari Game should end. When the player jumps off a ledge, they temporarily lose collision interactions with solid objects until they land on the lower ground, so if the game transitions to another map before the player can land, the collision interactions are never restored. To make extended use of this glitch, the player must also black out while inside the Safari Zone's entrance building after being warped back when the Safari Game ended.

To start this process, the player must first get a ed Pokémon and deposit all of their other Pokémon in the PC. Either the poisoned Pokémon must have high HP (over 124) or the player must have enough Potions to keep it from fainting too early.

The player must enter the with the poisoned Pokémon, paying 500 to play. Next the player must try to exit the Safari Zone, but when asked if they want to leave early, they must select no. Now, the player must save the game and restart. When the game loads, the player must again exit the Safari Zone, but this time, the attendant will treat the player as if they entered from Fuchsia City, and when the attendant asks if the player wants to play the Safari Game, the player must select no.

From there, the player must walk 499 steps, ending at a position in the city where they can jump off a ledge with one more step. (The poisoned Pokémon loses HP every four steps and causes the screen to flash, so it is possible to count 124 flashes and take 3 further steps. By the same token, it is also possible to calculate a loss of 124 HP for the poisoned Pokémon and track its HP.) If the poisoned Pokémon has less than 124 HP, a Potion must be used on it to prevent it from fainting.

After the player has walked 499 steps and is in an appropriate position, they must jump off the ledge so that they are in midair when they run out of steps for the Safari Game (with the glitched drop shadow sprite underneath the player). They will be warped back to the Safari Zone entrance building and the background music will stop. The player is now able to walk through walls, but attempting to leave the building without the doors at this point would cause the game to crash. Talking to the man will only cause him to say "Welcome to the Safari Zone" without actually asking if the player wants to enter. If the player enters the Safari Zone, they will have over 100 Safari Balls and possibly infinite steps, but the player can't walk through walls anymore. If the player walks around in the building until the poisoned Pokémon faints, they will black out and be warped to the last Pokémon Center they healed at, and from there they will be able to walk through walls anywhere outdoors. The glitch wears off when entering a door (the normal entrance square to the bridge to the S.S. Anne where the NPC normally stops you counts as a door).

While in this state, the player can still talk to NPCs and interact with them as normal. Trainer battles will still trigger (however, upon completion of the battle, normal collision effects will be restored) and normal chat dialogue will remain. The player can interact with the "on display" Pokémon in Fuchsia City where their only dialogue is "!". If the player heads to Cycling Road and finishes a trainer battle, they can walk around without a bike. If the player battles a trainer while standing on water, they will be unable to move in any direction without the use of Surf after the battle.

The player is also able to fly and retain the ability to walk through walls. Under certain scenarios, this glitch may trigger the Glitch City glitch.

Saving the game and reloading it restores normal collision effects. If the player stands on Cycling Road and saves and loads the game, they can walk around on Cycling Road without a bicycle. Saving and loading the game while on a water tile causes the player to be unable to move without the use of Surf. Saving and loading the game while standing on top of the guard to the S.S. Anne allows the player to enter the bridge and then the ship. If an NPC forces the player to move, the glitch is cancelled.

This glitch may also replace the sprites of some Trainers.

Trade evolution learnset oversight
Generation I Pokémon that can evolve by trading can be taught glitch moves through this glitch. This can be achieved by trading a trade evolution Pokémon from a Generation I game to a Generation II, at a level where its evolved form will learn a move not in Generation I. Trading the Pokémon back to the Generation I game will cause that move to become a glitch move.

For example, trading a level from  to  will make the  evolve into. Since it is level, it will learn. 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, so it will become.

Pokémon Bank hex:FF glitch Pokémon glitch
If a player attempts to transfer a Box 1 that has one Pokémon, an 'M (00) or 3TrainerPoké $ and eighteen Pokémon (in that order) through Poké Transporter and a 3DS Virtual Console versions of Red, Blue and Yellow, the Generation I game will be left with one 'M (FF) or Q ◣ which is an unstable hybrid Pokémon of 'M (00) or 3TrainerPoké $ with a blank OT, ID of 00000 and no moves.

This Pokémon can be used for the Pokémon merge glitch unless stabilized through Day Care back into 'M (00) or 3TrainerPoké $.