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Bugs:Pokémon Red and Blue

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This page details bugs of Pokémon Red and Blue.

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This page doesn't represent the glitchiness of the games.

Overworld bugs

Safari Zone Glitch

The Safari Zone Glitch is probably one of the most infamous bugs due to how early it was discovered. To perform it:

  • Go to the Safari Zone and pay to enter.
  • Once inside, go right back to the gate.
  • When asked if you want to leave, say no to be brought back inside the Safari Zone.
  • Once there, save the game. Reset the console and load the saved game.
  • Go back to the gate and this time you will be asked if you want to enter the Safari Zone. Say no and exit to Fuchsia City.
  • Walk around through the game world until you reach 500 steps.

The Safari Zone's bell will go off as if you ran out of time, and you will warp back to the gate. Once you leave, depending on where you were when you reached 500 steps (most towns do not trigger this glitch), you will end up in a completely random, unplayable assortment of tiles dubbed Glitch City by the Pokémon community. The only way to get out is to Fly or Teleport, as doors and caves don't work and the game crashes when attempting to leave the map boundaries.

In Red and Blue only, you could achieve the same effect by blacking out inside the Safari Zone. This method was fixed in Yellow, although the Save & Quit method described above works in all versions.

Some further implications of this are:

  • If the 500th step is above a ledge, so the character is in mid-air when the bell sounds, you will gain the ability to walk through walls upon returning to the Safari Zone gate. This ability fades the moment you exit to (what would be) Fuchsia City, but it persists if you black out inside the gate (by having your last Pokémon faint from poison damage), allowing you to freely traverse the overworld.
  • If the 500th step is during the sequence in Pewter City where the NPC guides you to the Pewter Museum of Science, upon exiting the Safari Zone gate you will appear back in Pewter City but the NPC, and the rest of the game, will glitch out completely.

Trainer-Fly glitch

The Trainer-Fly glitch quickly became famous because it allowed people to catch Mew for the first time, and unlike all the schoolyard rumors it actually works.

The basic gist of the glitch is that for trainers that have a sight range that spans the entire screen, if you scroll the trainer into view and step into its sight range, the script that makes the trainer see you can be interrupted in one of the following two ways:

  • Open the menu (there is a short window of input where you can open the menu before the trainer sees you), then Fly or Teleport away. Inside a cave, Dig or Escape Rope will work as well.
  • Get a wild encounter on the exact tile the trainer would spot you (through tall grass or inside a cave). The wild encounter takes priority over the trainer seeing you. From there, lose the battle by blacking out.

If done correctly, the trainer will spot the player (the ! sprite will appear over his head) but the player character will warp away before the trainer gets a chance to walk up to the player character.

Because the game still thinks that a trainer battle is about to take place, the menu will be disabled. The effects of this can be remedied by fighting a different trainer (in a different area than the one where the first trainer was encountered), making sure the trainer walks to the player character (if the player character engages the trainer directly or walks right in front of him without at least a tile of space in between, the game will softlock).

Once that is taken care of, walking back to the map where the first trainer was will open the menu automatically, then start a wild battle.

  • The species of the wild Pokémon is determined by the Special stat of the last Pokémon fought. As such, if the Special stat of the last Pokémon fought was 21 (hex 15), you will fight a Mew.
  • The level is determined by that Pokémon's attack modifier, which defaults to 7. By using Growl (or another Attack-lowering move) six times before ending the battle, you will fight a level 1 Pokémon, which causes various glitches as no Pokémon were ever intended to be encountered at level 1.

In Red and Blue, the earliest point in the game this can be used to catch a Mew is if the Jr. Trainer♂ on Route 24, directly west of Nugget Bridge is used as the first trainer, and the Swimmer inside Cerulean Gym, whose last Pokémon is a level 16 Shellder (Special of 21) is used as the second trainer. In Yellow, a Mew can be caught even earlier, using the Yellow-exclusive Bug Catcher in Viridian Forest as the first trainer, and the Super Nerd that protects the fossils in Mt. Moon as the second trainer.

A second, lesser known consequence of this glitch is that the game will remove one sprite from the overworld, because it makes the assumption that the wild Pokémon fought comes from a special one-time event (like the legendary birds or Mewtwo). This can be used to remove the sleeping Snorlax from route 12, eliminating the need to enter the Pokémon Tower and acquire the Poké Flute.

Unwinnable Game

Due to an oversight, it is possible to create an unwinnable game in all versions of Red, Green, and Blue. Around halfway through the game, you are required to pay 500 Poké Dollars to enter the Safari Zone in order to find HM03 Surf and the Gold Teeth (to give to the Warden for HM04 Strength), both of which are necessary to progress further into the game. If your money, the cumulative sell value of all your items, and the cumulative money yields of all available trainer battles total to less than 500 Poké Dollars, and you have no Meowth that can use Pay Day, the game becomes unwinnable.

This was fixed in Yellow by allowing you to enter the Safari Zone with fewer than 500 Poké Dollars:

  • If you have some money, you'll be given fewer Safari Balls proportional to the amount you paid.
  • If you have no money at all, bug the guard enough times and he'll let you in with one Safari Ball.
(Source: Pikasprey Yellow)

Man on the Roof Glitch

Pokemon RB man on roof.png

On Cinnabar Island, if the player doesn't have the Secret Key in the Bag and uses a Pokémon with Surf to surf on the east coast, then returns to the shore while near the Gym and walks in front of the Gym's door, an old man will appear on the roof of the Cinnabar Gym while the text box saying "The door is locked..." appears. After the text box disappears, the NPC will vanish.

There are other variations of this glitch, such as when pressing Start as soon as the player enters Nugget Bridge or Route 6. All variations were fixed in the European releases.

Escape Rope bug

In all versions of Red, Green, and Blue, you can use an Escape Rope to escape the Pokémon Fan Club in Vermilion City as if it were a cave. This was patched in Yellow.

Invisible PC bug

In Celadon Hotel, there's an invisible PC that can be used by walking to where the PC would be in a Pokémon Center (go to the very right of the room, stand one tile away from the counter and face up). Three of the four rest houses in the Safari Zone also have invisible PCs, though they cannot be accessed without using a walk-through-walls code.

Yellow removed all invisible PCs.

Battle Engine bugs

1/256 Miss Bug

Rather infamously, any move in the game, including those that have 100% accuracy, may miss at a rate of 1/256.

This happens due to a quirk in how the game determines whether a move should miss or hit. The algorithm rolls a random number and then checks if that random number is less than the move's accuracy (taking into account accuracy modifiers and such) to determine whether the move should hit. However, if the RNG rolls an FF, this condition can never hold true because there is no number higher than that, so any move will miss if that number is rolled by the game's RNG. The only move that is impervious to this bug is Swift because it bypasses the accuracy check to always hit, however this applies only to the international (non-Japanese) versions of the games.

Lorelei Softlock

In Red and Blue, it is possible to end up in a practically infinite battle if you challenge Lorelei with certain Pokémon that know the move Rage while all of its other moves have zero PP.

The reason for this is twofold: first is how the AI in Red and Blue works. While the AI used by wild Pokémon is fairly simple (it just selects any of its available moves at random), trainer AI on the other hand is forced to take type effectiveness into account and always chooses a move of a type super effective against the player's Pokémon, if available, even if that move is a status move (which will not deal damage).

In Lorelei's case, if the player sends out a Fighting- or Poison-type Pokémon (the two types weak to Psychic), Lorelei's Dewgong will use Rest continuously, because Rest is Psychic-type, and therefore the trainer AI is forced to select it (unless the Pokémon in question is also weak to the Ice-type Aurora Beam (which Lorelei's Dewgong knows), such as Nidoking (Poison/Ground), as there is a chance that the trainer AI will instead select that move). If the player's Pokémon cannot do enough damage to compensate for the amount restored by Rest, this results in the battle being unwinnable. Enemy trainers cannot run out of PP in these games, and there is no way to end the battle other than winning or losing. However, your Pokémon would eventually run out of PP, and trying to attack after this causes the Pokémon to use Struggle, which causes recoil damage, and this would eventually cause your Pokémon to knock itself out, ending the battle and causing the player to black-out, returning them to the last used Pokémon Center.

This is where Rage comes in, the second key necessary for this softlock. In Generation I games, when selecting Rage, one PP is consumed, and then the Pokémon is forced to continuously use Rage thereafter as long as the move doesn't miss the first time (bare in mind that Rage has 100% accuracy); however, these forced uses of Rage do not consume PP, even if a forced use of Rage misses, rendering the Struggle problem moot. Saving the game before entering the battle under these conditions effectively dooms the save file, as leaving the room Lorelei is in is only possible by winning or losing the battle against her.

That said, the above situation is technically escapable due to an infamous bug in Generation I where every move in the game, even ones with 100% accuracy, have a 1/256 chance of missing, including Rage. Therefore, triggering this miss 20 times in a row will deplete Rage's PP, causing the Pokémon to knock itself out with Struggle. The chance of missing 20 times in a row at these odds is astronomically unlikely (1/256^20) with a probability of practically zero.

Yellow fixed this conundrum by programming in a special case for Lorelei's Dewgong, which allows the AI to break out of the above logic and select a random move from its move pool 40% of the time.

(Source: Pikasprey Yellow)

Evolution Stone bug

Pokémon that normally evolve by Evolution Stone will also evolve if they level up in battle and the last Pokémon sent out in that battle has the same index number as the evolution stone. The Pokémon correspond to the Evolution Stones as follows:

  • Moon Stone (0A): Exeggutor
  • Fire Stone (20): Missingno. (not normally obtainable)
  • Thunderstone (21): Growlithe
  • Water Stone (22): Onix
  • Leaf Stone (2F): Psyduck

This bug was fixed in Yellow.

Ghost Marowak bugs

The fight with the ghost Marowak in Pokémon Tower, when its identity hasn't been revealed with the Silph Scope, is particularly buggy in this game.

  • Just triggering this fight will register Marowak as seen in the Pokédex.
  • If you check out one of your Pokémon's stats during battle, the ghost sprite will revert to the Marowak sprite. This is a purely visual bug, you still can't attack the ghost Marowak.
  • Using a Poké Doll ends the battle as if you won, progressing the game's storyline. This completely eliminates the need to acquire the Silph Scope, skipping the entire Rocket Hideout in the process.

Psywave bug

The special RNG algorithm that calculates Psywave's damage will discard a 0 if the player is the user but not if the player is the target. If this occurs in a link battle, the link battle will desync.

Fly/Dig Invulnerability bug

If a Pokémon uses Fly or Dig and the attacking turn fails due to confusion or paralysis, the Pokémon will become invulnerable for the rest of the battle until they use Fly/Dig or a charging move (Razor Wind, Skull Bash or SolarBeam).

Healing Moves bug

Healing moves (Recover, Rest, or Softboiled) will fail if the difference between the current HP and max HP is exactly 255 or 511. That is because the algorithm that determines if the move should fail due to the Pokémon already being fully healed erroneously doesn't take the upper bits of the HP value into account and only checks the lower bits.

Focus Energy bug

The move Focus Energy is completely broken in these games; instead of increasing the critical hit chance, it reduces it to a quarter of its original value.

The game's code reveals that the two branches that determine critical hit chance may have been accidentally swapped; if so, the reduced critical hit chance might have been the originally intended critical hit chance and the critical hit chance of the final game would have been the one after using Focus Energy. Thus, critical hits would have been a lot less common than they ended up being in the final game.

This bug also applies to the Dire Hit item, which uses the same function as the Focus Energy move.

Hyper Beam bugs

The move Hyper Beam comes with another set of bugs:

  • If the player's Pokémon uses Hyper Beam, then gets frozen before it gets to its recharge turn, the player will stop getting turns altogether, allowing the enemy to attack endlessly until the player's Pokémon faints or gets thawed from a Fire-type move. The move Haze will thaw the Pokémon but not end the glitch, so the player will still not get any turns.
  • If the player's Pokémon uses Hyper Beam, and the opponent attempts to use a binding move (Bind, Clamp, Fire Spin or Wrap) and it misses before the player's Pokémon gets to its recharge turn, the player's Pokémon will automatically use Hyper Beam again instead of recharging. If the move has 0 PP at this point, it will roll over to 63 PP.

Transform bugs

The move Transform is particularly buggy in these games:

  • If the player's Ditto uses Transform, and then you use the Select button to swap the first move with a different move in the transformed Pokémon's moveset, once the battle ends the Ditto will have Transform replaced with the glitch move -- (two dashes), which corrupts the game when used. This was fixed in Yellow.
  • If a wild Pokémon uses Transform and is caught while transformed, it will become a Ditto even if it was originally a different species. This can only happen when a Pokémon uses Transform by way of Mimic, Mirror Move or Metronome, as the only Pokémon that learn Transform are Ditto and Mew, and the latter cannot be legitimately encountered in the wild.
  • If a Pokémon that used Transform levels up during battle and learns a new move, the transformed moveset will be replaced by its own moveset, even though the Pokémon will otherwise stay transformed.
  • If a transformed Pokémon uses Metronome or Mirror Move, the Pokémon will gain 1 PP in the moveslot corresponding to its own moveset. If there is no move in that moveslot, the Pokémon is effectively locked out of Struggle forever. This can also lead to a softlock if the Pokémon has no usable moves and the enemy Pokémon attempts to use Disable.
  • In SGB mode, any Pokémon that is not Ditto and uses Transform will have its sprite's palette replaced with Ditto's if the sprite is refreshed by opening the menu and checking out a Pokémon's stats.

Substitute bugs

The move Substitute comes with its own set of bugs:

  • If the user's current HP is exactly 25% of its maximum HP, using Substitute will leave the Pokémon with 0 HP, fainting immediately.
  • If both the player and the opponent have a Substitute up and the player's Pokémon hurts itself due to confusion, the opponent's Substitute will take the confusion damage instead. If the opponent does not have a Substitute, the damage gets discarded entirely.
  • If Explosion or Selfdestruct are used against a Substitute and the Substitute breaks, the user will not faint, but its sprite will vanish and it will be invisible for the remainder of the battle. Similarly, if a move that hits with recoil breaks a Substitute, the user will not take any recoil damage.

Toxic bugs

  • The damage multipliers used by Toxic and Leech Seed will stack with one another if both are inflicted on the same Pokémon. This is because both moves use the same variable for determining how many turns have passed since the move was used.
  • If a Pokémon affected by Toxic uses Rest, it will no longer be badly poisoned but the turn counter will not be reset. If the Pokémon then gets affected by Toxic or Leech Seed again, the damage multiplier will pick up where it left off. Additionally, if the Pokémon gets burned instead, the burn damage will behave like Toxic and increase with each successive turn.

Blaine AI bug

Blaine has two Super Potions that he can use on his Pokémon. However, because there is no check for the Pokémon's HP, he will try to use the Super Potions even on Pokémon that have full HP.

This was fixed in Yellow, so it was very likely not intentional.

Cooltrainer AI bug

The Cooltrainer♀ has special programming where if its Pokémon's current HP is between 10% and 20% of its max HP, it will switch it out. If two of its Pokémon meet that condition, it will switch them with one another every turn and never attack. This behavior was supposed to only happen 25% of the time, but due to a programming bug, the RNG roll is completely discarded and the behavior will always happen as long as the conditions are met.