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Pokémon Red and Blue/it

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This page is a translated version of the page Pokémon Red and Blue and the translation is 6% complete.

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Title Screen

Pokémon Rosso e Blu

Also known as: Pocket Monsters: Red & Green (JP), Pocket Monsters: Blue (JP)
Developer: Game Freak
Publisher: Nintendo
Platforms: Game Boy, Super Game Boy
Released in JP: February 27, 1996 (Red & Green), October 15, 1996 (Blue)
Released in US: September 30, 1998
Released in EU: October 5, 1999
Released in AU: October 23, 1998

AreasIcon.png This game has unused areas.
CodeIcon.png This game has unused code.
DevMessageIcon.png This game has a hidden developer message.
DevTextIcon.png This game has hidden development-related text.
GraphicsIcon.png This game has unused graphics.
ItemsIcon.png This game has unused items.
MusicIcon.png This game has unused music.
TextIcon.png This game has unused text.
DebugIcon.png This game has debugging material.
RegionIcon.png This game has regional differences.
Carts.png This game has revisional differences.

Pokémon Rosso e Blu, usciti per la prima volta in Giappone con il titolo Pocket Monsters: Rosso e Verde, e più tardi anche come Pocket Monsters: Blu, sono i capitoli originali della serie Pokémon che hanno incollato molti ragazzini agli schermi dei loro Game Boy mentre cominciavano la propria avventura per diventare campioni di Pokémon.

Gotta catch 'em all!

To do:
La pagina di Giallo non dovrebbe essere unita a questa, considerando che sono tutti e tre lo stesso gioco?


Errori di traduzione
Errori presenti nei testi del gioco quando fu tradotto da un linguaggio all'altro.
Differenze tra le versioni
Differenze varie tra le versioni, comprese alcune di localizzazione.


Ordine originale del Pokédex

Farei carte false per quel raccoglitore.

Unlike later games, the internal Pokémon species table is far from sorted: they aren't grouped by their evolutionary families nor any other reasonable order. For example, index numbers 0x01, 0x02, and 0x03 are Rhydon, Kangaskhan, and Nidoran♂. This is likely an early Pokédex order, or even the order in which the Pokémon were originally added to the game.

One special episode of Game Center CX features an interview with Pokémon creator Satoshi Tajiri. During the interview, a possible early design document or proposal for the games is shown complete with close-up shots of three different Pokémon: Nidoking, Slowbro, and Kadabra. The documents depicted the Pokémon sprites from Red and Green as well as their names and Pokédex numbers. Interestingly, the numbers do not match up with the final Pokédex order but rather the internal species table, placing Nidoking at 0x07, Slowbro at 0x08, and Kadabra at 0x26. It can also be assumed that those screens come from a very early version of the in-game Pokédex function, considering the layout of the screen and the faintly visible Super Game Boy border.

È di nota anche il nome originale di Nidoking che, a differenza quello finale, ニドキング (Nidokingu), qui è マイコー♂ (Maiko♂).

In addition, the species table has 190 entries, 39 of which are completely blank and result in the game loading MissingNo. (see below) instead. Words from Shigeki Morimoto have supported that there were once 190 Pokémon planned for inclusion in the games.


To do:
  • A thorough explanation of what data is organized by index number and what data is organized by Pokédex number so that the differences and similarities between MissingNo. and 'M are clearer.
  • .ogg file for 0x45; the cry is exactly identical to Zubat's. See also: This needs to be incorporated into the article.
  • And most other stuff on the talk page.
MissingNo.'s Cries
ID Cry

Arguably the most (in)famous glitch/leftover in any game, MissingNo., short for "Missing Number", is used to fill the 39 empty slots of the 190-slot Pokémon species data table. The glitch was made famous when players discovered a way to encounter it by exploiting a programming oversight in said data table for helpful side effects. The land/water border tiles on the east coast of Seafoam and Cinnabar Islands are set to generate random wild Pokémon encounters from the current location (as grass tiles do) rather than with water Pokémon. Since these areas do not have random wild Pokémon encounter data, the data from the previous area is left in memory. In the Japanese version, its name is けつばん (Ketsuban), which literally translates into "missing number."

witty caption to be written

Base Stats

The aforementioned Pokémon species table has 39 entries which give MissingNo. a Pokédex number of #000. As the base stats are ordered by Pokédex number as opposed to index number, this results in all the 39 MissingNo. copies sharing the same type (Bird/Normal), stats, start moves, graphics, etc. None of this data is actually valid; the game reads data that is stored far outside the base stats table and is actually used to define the parties of trainers. In the Japanese Blue, MissingNo. points to data that defines it as a ??? Pokémon, with a height of 1.0 m (3.3 ft) and 10.0 kg (22.1 lb), as well as a filler Pokédex entry saying 「コメント さくせいちゅう」 "Komento sakusei-chū", which translates into "Comment to be written". This information was not translated in the English localization and hence displays the erroneous values of 10.0 ft (3.1 m) for the height and 3507.2 lb (1590.8 kg) for the weight when its Pokédex entry is viewed.

Old Man Glitch

During the old man's Pokémon-catching tutorial in Viridian City, the player's name is changed to "OLD MAN". The original name is copied into the wild Pokémon encounter table for temporary storage. As soon as the player enters an area with wild Pokémon encounters, the table will be repopulated, so this normally has no effect on the game. However, taking advantage of the incorrect water tile assignment allows players to encounter wild Pokémon while the encounter table still contains the player's name. The letters of the name then define which Pokémon will appear and at which levels; several letters correspond to invalid IDs, leading to encounters with MissingNo., 'M, or glitched Trainers at impossibly high levels. In the Japanese version this does not work, and no encounters of any kind will occur on the affected tiles.

Item Duplication

Contributing to MissingNo.'s fame is the item duplication glitch. Any time the player encounters MissingNo., 'M, or any other glitch Pokémon with Pokédex number 000, the game attempts to set the "Pokémon has been seen" flag for that Pokémon in the Pokédex. Due to an integer underflow when calculating the address of this flag, it instead sets the highest bit of the quantity of the sixth item in the player's Bag, effectively adding 128 to it. If you catch it, the sixth item duplicates again (assuming it's been reduced to less than 128).


The glitch Pokémon 'M (actual name consisting of corrupted graphics with 'M in the middle) is often confused with MissingNo., as they are both commonly found using the Old Man glitch and both have the Pokédex number 000, giving them the same in-battle sprite and base stats, and causing the item duplication glitch. However, 'M is not pulled from unused Pokémon data like MissingNo. but from other data located after the Pokémon data in ROM instead. Its similarities to MissingNo. are coincidental.


Most variations of MissingNo. have similar appearances to the screenshot above, but it can also assume the sprite of one of the fossils in the Pewter City museum or a Pokémon Tower ghost depending on various factors. (It should be noted that in the Japanese versions of the games, a ghost MissingNo. is referred to not as けつばん but by the otherwise unused string of "ゴースト" - distinct from actual Pokémon Tower ghosts, which are called "ゆうれい".) Each MissingNo. also has a separate cry. Most of these are simply set to three zeros, resulting in its cry sounding similar to Nidorin♂'s cry, however there are a few unique ones (see here). Each individual MissingNo. entry has a unique, empty move-learning and evolution table, further suggesting that these slots belonged to deleted Pokémon. Additionally, MissingNo.'s name is repeated 39 times in the ROM, once for each entry.

For further technical details, see here and here.

Unused Game Mechanics

Bird Type

The BIRD type.
There is an unused Bird type for Pokemon within Red and Blue. It has no weaknesses or resistances, and only certain glitch Pokemon like MissingNo. have this type. It remains, still unused, in Pokémon Gold and Silver.

Extra Field Move

In the list of field moves, there is an unused entry between Fly and Surf. It points to an empty string in the field move name table. It has a move ID of 0xB4, although the highest valid move ID is 0xA5, suggesting that there were moves removed before the games were released. Its position in the list of field moves, between two HMs (all HMs are in order) suggest this may have once been an HM.

At offset 0x80096 is the unused text string "Ground rose up somewhere!", which is located near the string used when using Strength. It has been suggested that it was originally intended to be used for a field move.

(Source: Sawakita)


The "YES/NO" options replaced by the "NORTH/WEST" options

In addition to the normal options such as "YES/NO" and "HEAL/CANCEL", additional options "NORTH/WEST" (Japanese: きた/にし), "NORTH/EAST" (Japanese: きた/ひがし) and "SOUTH/EAST" (Japanese: みなみ/ひがし) are present but never used. "NORTH" and "EAST", while referenced in the Safari Zone, are found within strings of text rather than as options.

NORTH/WEST can be seen with GameShark code 01012CD1, NORTH/EAST can be seen with GameShark code 01042CD1 and SOUTH/EAST can be seen with GameShark code 01022CD1.

Default Total PP of Struggle

To do:
Where did this even come from? My sources say it's defined as 10 in the generic move data structure, but when loaded it's loaded as 1.
Struggle is a move which cannot be learned during regular gameplay. It is only used when the user's Pokémon attempts to attack but has no available PP for any move left (note that in-game Trainers cannot run out of PP in Generation I). Regardless, the default total PP data for Struggle is referenced as 1, though there is a special handler for Struggle such that its remaining PP remains at 1 regardless of how many times the move is used.

The default total PP for Struggle has remained at 1 in all the main series handheld Pokémon games as of Generation V.

Unused Battle AI

To do:
Is this list exhaustive (I'm pretty sure it's not)?
There is data for unused battle AI which is normally never applied to any Trainer class, including "use X Accuracy" and "use Dire Hit".
(Source: Pokémon Red disassembly project)

Dragon Type is Super Effective against Itself

As with every subsequent generation, the Dragon type does super-effective damage to itself in Generation I. However, the only Dragon-type move in Generation I is Dragon Rage, which does a set regular damage of 40 HP, and hence this behavior is never seen in regular gameplay during this generation.

Unused Move Effects

To do:
Is this list exhaustive?
There are a handful of effects in English Red and Blue which aren't used by any valid move, although some of these are used by the TM(xx) and HM(xx) glitch moves. Note that in the Japanese versions, effect 23 (30.1% freeze chance) was used because the effect was assigned to Blizzard (see here).
Identifier Effect
01 Puts enemy to Sleep.
0C Raises Speed by 1 stage.
0E Raises Accuracy by 1 stage.
15 Lowers Special by 1 stage.
17 Lowers Evasion by 1 stage.
1E Attacks for 2-5 turns.
23 30.1% chance of freezing the opponent.*
36 Raises Accuracy by 2 stages. (probability=hit chance)
37 Raises Evasion by 2 stages. (probability=hit chance)
3A Lowers Attack by 2 stages. (probability=hit chance)
3C Lowers Speed by 2 stages. (probability=hit chance)
3D Lowers Special by 2 stages. (probability=hit chance)
3E Lowers Accuracy by 2 stages. (probability=hit chance)
3F Lowers Evasion by 2 stages. (probability=hit chance)
48 10.2% chance of lowering Accuracy by 1 stage.
49 10.2% chance of lowering Evasion by 1 stage.
4A None.
4B None.

Butterfree for Beedrill in-game Trade

There is an unused in-game trade in which the player would trade a Butterfree for a Beedrill, which was carried over from the Japanese Red and Green. In those versions, the traded Beedrill was originally nicknamed ピピん (Pipin); however, in the Japanese Blue (which the international Red and Blue are mainly based upon), its nickname was changed to チクチク (Chikuchiku).

As such, there is unused text in the English Red and Blue for a Beedrill nicknamed "CHIKUCHIKU".

Unused Items

There are several unused or dummied-out items in the games. These remain present and unaltered in Yellow.

  • Coin (3B) - These items will stack but cannot be used (attempting to use it will bring up Professor Oak's unusable message) or stored into a Coin Case. Coins can be sold at a PokéMart for 5 Pokédollars per coin. If hacked into a PokéMart listing they are sold for 10 Pokédollars each.
  • False PP Up (32) - For unknown reasons, there are two PP Up items stored in the game, 32 and 4F. 32 is a fake PP Up which cannot be used (attempting to use it will bring up Professor Oak's unusable message). It can, however, be sold at a PokéMart for 4900 Pokédollars or purchased for 9800 Pokédollars if hacked into a PokéMart listing. Amusingly, the real PP Up has no value and can only be purchased/sold for 0 Pokédollars.
  • ????? (07) - An item with a dummied-out name. Using it is similar to using Surf from a Pokémon, but it can be used without any badges (or indeed any Pokémon). Additionally, it can be used on Cycling Road without receiving the "Cycling is fun! Forget SURFing!" message. Either HMs didn't exist early in development, there were abandoned plans for a surfboard item, or this is a testing item. Additionally, attempting to use this item while already surfing and while facing land will cause the game to lock-up with the item name tile graphics messed up. The music updates as if the player was not surfing in the location the item was used. Internally, the actual effect of Surf is implemented by using this item. This is not the case for any other HM move, though it is similar to the out-of-battle effect of Dig, which is handled by using an Escape Rope.
  • ????? (2C) - Also has a dummied-out name, but in this case attempting to use it does nothing except giving Professor Oak's unusable message regardless of whether the player is in battle, suggesting that it might be a dummied-out key item.
  • TM51–TM55 (FB-FF) - Contain the relevant HM moves, in order (e.g. TM51 teaches what HM01 would teach ― Cut). They work pretty much as expected, teaching a compatible Pokémon the appropriate move. Unlike the corresponding HMs, TM51-55 will stack and can be sold at a PokéMart. TM51 sells for 1500 Pokédollars (PokéMart price: 3000 Pokédollars), TM52 sells for 7000 Pokédollars (PokéMart price: 14000 Pokédollars ― appears as a glitchy tile followed by three 0s), TM53 sells for 0 Pokédollars (PokéMart price: 0 Pokédollars), TM54 sells for 4000 Pokédollars (PokéMart price: 8000 Pokédollars) and TM55 sells for 2000 Pokédollars (PokéMart price: 4000 Pokédollars). TM55 is actually used as the Cancel function ― it appears as Cancel and hides items below it.

Unused Trainer Classes


Pokemon chief.png

Triggered by an hexadecimal identifier of 0xE3. It actually has no sprite, but uses the Scientist Trainer class sprite because its identifier is directly before it (0xE4). No rosters appear to be defined, meaning 'its first roster' is the first Scientist's roster. The Chief has not been found to give any valid victory speeches when defeated. Despite this, he is still mentioned in-game by a Team Rocket Grunt in one of the houses near the hotel in Celadon City, whose dialogue is "CHIEF! We just shipped 2000 POKéMON as slot prizes!"

Interestingly, the Japanese name of the Chief Trainer class is "シルフのチーフ" (Shirufu no Chīfu), which translates to "Silph's Chief". This implies that the player was originally meant to battle Silph Co.'s president.

Professor Oak

Pokemon oak.png

A battle with Professor Oak is programmed in, although he never actually battles the player during regular gameplay. The battle can be triggered with GameShark code 01E2D8CF (where the level of what would be a wild Pokémon corresponds with the roster value), or by using one of various glitches in the game. His name appears as "PROF.OAK" (Japanese: "オーキドせんせい" aka "Ōkido-sensei", rather than the normal "オーキドはかせ" aka "Ōkido-hakase").

Oak is programmed with three different teams, each consisting of a Level 66 Tauros, a Level 67 Exeggutor, a Level 68 Arcanine, and a Level 70 Gyarados. His fourth Pokémon is Level 69 and is either a Venusaur, Blastoise, or Charizard. It is assumed the game would choose the team with the final evolution of the starter Pokémon that neither the player nor the rival chose. Additionally, based on this team and their levels, it's likely he was supposed to appear at the very end, perhaps even after the final rival battle at Indigo Plateau. When defeated and counting the fact that Professor Oak used one of the valid rosters mentioned above, he will give whatever dialog that the Trainer you used to fight him says when defeated. This means that he has no real "lost battle" dialogues of his own programmed in.

It is possible to battle him using the Ditto glitch (an extended version of the Mew glitch) with the last Special stat in memory as 226. He can be encountered (though without his appropriate roster) as a glitch Trainer while doing the Old Man glitch and having the MN symbol in the third, fifth, or seventh slots of the player's name. Another way of battling him is this select button glitch in Japanese Red, Green and Blue.

The data for this battle remains present in Yellow. The concept of battling a Pokémon professor would later be reused in Pokémon X and Y.


Deleted Maps

There are 26 deleted map locations, though header data still exists with the exception of a tentative unused town with its own Fly flag. All of these freeze the game when accessed.

  • Three deleted maps using the Victory Road map header, with identifiers 0x69-0x6B.
  • 17 deleted maps using the Pokémon League map header, with identifiers 0x6D-0x70, 0x71-0x75, and 0xED-0xF4.
  • A deleted map using the Pokémon Tower map header, with identifier 0x94.
  • Three deleted maps use the Rocket HQ map header, with identifiers CC-CE.
  • A deleted map using the Rock Tunnel map header, with identifier E7.

Extra Town?

Map 0x0B is stored alongside city/town maps (0x00-0x0A; routes start with Route 1 at map 0x0C) and has Town Map location data as a town (not as a route) north of Indigo Plateau, since an unused flag when checked allows the player to Fly to it. It erroneously appears north of Indigo Plateau because its coordinates are undefined, leading the game to fallback to coordinates (0,0). The relevant Town Map name is also presumably undefined and shares its name with prefix 0x00: Pallet Town. Additionally, no Pokémon appear in map 0x0B. From this, it can reasonably be concluded that there was at one point another town in that location, removed from the final releases.

Celadon House

Location of the deleted entrance
An unused warp exists in Celadon City where the door to a house would be, but the door is not found in the final game. The warp leads to the fifth floor of the Celadon Department Store (map 136).

Since it would be unreasonable to end up on the fifth floor of somewhere from Celadon City and not the first floor, it may suggest that map 136 was altered at some point in the game's development. Further supporting this theory, the other floors (in order) for the Celadon Department Store have index numbers 122-125 respectively. The fifth floor (map 136) does not follow this pattern.

Exit location data exists for the map (the exit point index number is 08).

You can create a door to access the warp with the GameShark code 017C72C8. You can appear where the warp is by using the GameShark codes 0108B5D3 0108B1D3, entering a certain map in Celadon City (such as the Pokémon Center) and exiting.
(Source: Torchickens/IIMarckus)

Unused Alternative Maps

For unknown reasons, complete maps exist within the games which correspond to real locations, but these corresponding maps use different theme music for what was actually used for the same location in the final releases. These maps can be accessed via the map location modifier code 01XX5ED3.

Location Used map identifier Corresponding unused map identifier Music of used map Music of the corresponding unused map
House robbed by a Team Rocket Grunt in Cerulean City 0x3E 0x49 Cerulean City Theme Caves of Mt. Moon
Underground Path entrance (Route 6) 0x4A 0x4B Pewter City Theme Vermillion City Theme
PokéMart in Cinnabar Island 0xAC 0xAD Pokémon Center Cinnabar Island Theme
(Source: Glitch City forums)

Duplicate Diglett's Cave Map Data

There are two copies of the map data for Diglett's Cave in the English Red and Blue (and probably other localizations too). In these versions, the maps are at ROM offsets 0x60258 and 0x61F86.

Hidden Items in Unused Maps/Misplaced in Maps

Location of the inaccessible Nugget in Safari Zone entrance
To do:
  • Show where the coordinates are located on the map (since it's a small enough map, it should be okay).
  • Verify map id 0x6F is unused before adding its hidden item.
In certain areas around the Safari Zone entrance, using your Itemfinder causes it to tell you there is a hidden item nearby, which is unobtainable. The item is a Nugget, located at the coordinates (10,1). This suggests that the map was changed during development without the hidden item being removed, as hidden item data is separate from other map data.

Pokémon Center data in other maps

Pokémon Center data including triggers for PCs can be found in maps that are not used as Pokémon Centers in Red and Blue. As there is no PC sprite, the PCs are invisible. All of the hidden PC triggers were removed in Yellow.

Celadon Hotel

The Celadon Hotel has an invisible PC in the same position as a Pokémon Center.

Safari Zone rest houses

Unused code suggests that 3 of the rest houses in the Safari Zone, specifically maps DF, E0 and E1 were intended to function as Pokémon Centers. Each map has a trigger for an invisible PC in the same position as a Pokémon Center. Additionally, when healing at a Pokémon Center, the game saves your current location as the place to return to when using e.g. Teleport. The code checks if you're in one of the rest houses, and if so will not save your location.

(Source: stag019 (Safari Zone information))

Unused Song

Game Genie

Red and Blue both contain a short unused song with no defined pointers. As it only has two channels, with the octaves are set too high and one channel that goes off-sync with the rest of the music, the song appears to be incomplete. The song is defined in the ROM with a relatively high tempo. The addresses for the two channels can be heard and are stored in the ROM at offsets 0xA913 and 0xA9CF, respectively. The restored version of the track gives an idea of how the song should have been:

Damaged Restored

The song can be patched to Pallet Town by changing offsets 0x822F to 13, 0x8230 to 69, 0x8232 to CF, 0x8233 to 69, 0x8235 to 6F and 0x8236 to 6A. Game Genie equivalent at the left.

(Source: Restored by Koolboyman)

Unused Functions

Unused functions and subroutines in the program.

Debug Mode

Setting bit 1 of RAM address D732 enables some debug features:

  • When starting a new game, most of Oak's intro speech is skipped, including the player and rival name selections. Their names are set to "NINTEN" and "SONY" respectively.
    • In the original Red and Green, the player is named やまぐち (Yamaguchi, named after Wataru Yamaguchi, who is listed in the game credits under Special Thanks), and the rival is named いしはら (Ishihara, named after Pokémon developer Tsunekazu Ishihara).
    • In the Japanese Blue, the player is named ゲーフリ (Gēfuri, an abbreviation of "Game Freak"), and the rival is named クリチャ (Kuricha (creature), a reference to Creatures Inc.)
  • When starting a new game, the player starts outside their house, rather than in their bedroom.
  • Holding B prevents wild Pokémon encounters.

The Gameshark code 010332D7 will enable this, but may have other side effects, such as not forcing a bicycle on Cycling Road, and some warps not functioning correctly. (These are due to the code changing other, unrelated bits of the same address.)

(Source: IIMarckus (default names) & Pokemon Red Disassembly (debug flag))

Error Codes

PokemonRed ERROR code.png
Error codes are messages that appear when a 00 character appears in the middle of a text string. Error codes appear in the format "(X) ERROR." In Pokémon Yellow, they appear in the format "(X) error." (X) is a number normally representing the identifier of the text string. When an error message is printed on the screen, all text after the 00 character is ignored, however it's possible for other text to precede the error code, causing confusion ("54 error" vs "4 error" which happens to have a "5" before it). Error codes may appear during the Trainer-Fly glitch. For example, fleeing from the long-range Trainer on Route 6, re-enabling the ability to use the start menu with a Trainer in a location other than Route 6 and returning to Route 6 after reading the PokéMart sign in Vermilion City will bring up a '9 ERROR.' as shown in the picture on the left. This is because the PokéMart sign has a text identifier of 09, stored in the memory address CF13, so the game attempts to load the last text box ID in memory. The corresponding text for Route 6 doesn't exist and is presumably just a single 00 character, so the game prints a '9 ERROR.' The PokéMart sign in Yellow has a text identifier of 0B, which coincidentally does not give an error message, though the 'VERMILION CITY The Port of Exquisite Sunsets' sign has an identifier of 08 and brings up a '8 ERROR.' upon returning to Route 6.

Gift Pokémon Function

In Japanese Red and Green, an unused function exists at ROM addresses 01:645C (Red v1.0), 01:645D (Green v1.0), 01:6401 (Red v1.1) or 01:6402 (Green v1.1), that adds three Pokémon to the player's party:

  • Exeggutor, level 90
  • Ekans, level 90
  • Rhydon, level 5

In Japanese Blue, the function is at 01:656F and adds three Pokémon to the player's party:

  • Exeggutor, level 90
  • Chansey, level 100
  • Rhydon, level 5
(Source: Glitch City Laboratories Forums)

In the English Red and Blue, the function is at at ROM address 01:64CA and adds five Pokémon to the player's party:

  • Exeggutor, level 90
  • Mew, level 20
  • Jolteon, level 56
  • Dugtrio, level 56
  • Articuno, level 57
(Source: Pokémon Red disassembly project)

In an interview with Pokémon developer Tsunekazu Ishihara, he states that Exeggutor is his favorite Pokémon, since he used it while debugging the game. This may explain the first entry in the list.

Unused "Battle Test" Function

To do:
Check whether the code exists in non-English translations. It seems to have been removed in Yellow, but it could still exist in an altered form.
This code was likely intended for debugging purposes. It can be accessed by running the code at 01:4DA6. This requires a bank switch, which is possible via the bank switch function at $35D6 (see here for the location in other regions/revisions), which sets the bank to what register c is, and jumps to hl.

It sets the badges value to $80 (effectively giving you the Earth Badge and no other badges), sets your current location to Pallet Town (though you can't see it), removes your current party Pokémon, and prompts you to nickname a level 20 Rhydon. Whether you give it a nickname or not, it will start a battle against another level 20 Rhydon. All four of your available moves only act like Pound, though this doesn't apply to the opposing Rhydon. After the battle (regardless of the outcome), the nickname prompt appears again and the entire process repeats.

The code exists in Pokémon Red and Green too, at 01:4B8D, where it seems to work the same.

(Source: Glitch City Laboratories Forums)

Game Boy Color detection

At the very beginning of the program (ROM address 0150), the game checks if it's running on Game Boy Color, and stores the result of this check at RAM address CF1A. However, the check stores zero in both cases:

cp a,$11 ;GBC can be detected by value of A register at boot
jr z, .gbc
xor a, a ;If not GBC, A = 0
jr .ok

ld a, 0 ;If GBC, A = 0

ld [$CF1A], a

The use of two different methods to set A=0 (single-byte xor a,a instruction vs the two-byte ld a,0) suggest that this check may have been quickly patched out. In any case, a few instructions later the init process clears all memory, so this flag gets reset either way.

If this flag is set, the game loads a set of monochrome palettes and skips loading Super Gameboy features, so it looks the same as it would on a regular Game Boy.

Unused Graphics

To do:
Figure out what the other missing blocks in tilesets 03, 06, 0B, 0C, 0D, and 10 are.
Red, Green, Blue, and Yellow have many tileset blocks that are never used in any existing map. Tileset 13 was added in Pokémon Yellow.
Identifier Unused Tiles Tileset
03 23, 2E, 30-32, 34-35, 37-3A, 3C-3D Pokemon RBY Tile Set 03.png
06 03, 05-09, 0B-0E, 10-11, 19, 20, 23-26, 2D-34, 39 Pokemon RBY Tile Set 06.png
0A 1A, 30-32, 4E, 5F-7B Pokemon RBY Tile Set 0A.png
0B 28, 30, 32, 4B-4C, 75-76, 78 Pokemon RBY Tile Set 0B.png
0C 0F, 18-1A, 22-24, 26-30, 32, 34, 40-46, 48-4A, 6B Pokemon RBY Tile Set 0C.png
10 1F, 23-27 Pokemon RBY Tile Set 10.png
11 0C-0D, 1D Pokemon RBY Tile Set 11.png
13 03-04, 08, 0E Pokemon RBY Tile Set 13.png

Outside the S.S. Anne

Unused Tiles

A sign is present in this tilemap but is unused, other maps do use the graphic though.

Identifier Tileset
04 Pokemon RBY Tile Set 04.png

Out Of View Graphics

There is a truck and boxes on the map that cannot be seen normally at the St. Anne dock.

And there's no Mew under the truck!
Give that player a cookie!
The truck in the Game Boy Advance remake.

It is possible to see them using tricks, however:

  • You must be one block above and one block to the left of the guy who checks the ship's tickets. Now walk one block to the right and then press start immediately after you come to a stop. Now save and restart your game, your character should be facing right. Now use the HM Surf and you will surf onto the ticket checker; press Down to bypass him.
  • You acquire a Pokemon with the HM Cut through a trade. This bypasses getting the HM on the ship which as a result makes the ship leave. You then obtain the HM Surf later and you can now surf to see the truck.
  • Acquire the HM on the S.S. Anne and lose to a Pokemon battle. Come back to the ship once you can use surf.

Despite rumors, the truck is only decoration and does not have anything hidden around or under it, save for a Lava Cookie in the GBA remakes.


The cave tileset contains some graphics that resemble the standard rock graphics, but they appear to be shinier and transparent, suggesting that it might be ice.

Identifier Tileset
0D Pokemon RBY Tile Set 0D.png
Pokemon RBY cave ice.png

Underground Path

The underground tunnel appears to be missing some graphics for the wall.

Identifier Tileset
12 Pokemon RBY Tile Set 12.png

Below is a recreation of how the tiles may have been arranged. It appears it was intended to have some sort of lighting fixture on the wall.

Original Mockup
Pokemon RBY underground path original.png Pokemon RBY underground path mock up.png

"Pocket Monsters!" Border Tiles

To do:
Game Genie codes to restore the original logos.
For some weird reason, the US Red and Blue still have the full tileset of the original Japanese "Pocket Monsters!" logo for the Super Game Boy borders. The European versions overwrote the logo as needed.
Red Blue
Pokemon Red U SGB Unused Pocket Monsters tiles.png Pokemon Blue U SGB Unused Pocket Monsters tiles.png
(Source: nensondubois)

Miscellaneous Findings

Placeholder Dialogue

Hey! How'd you get in here?
Using a walk-through-walls cheat to enter the Pokémon exhibits outside of the Safari Zone entrance and attempting to talk to the Pokémon in them reveals that they have placeholder dialogue programmed in, most likely in order to prevent crashing. This dialogue can also be seen when attempting to talk to a trainer in the Cable Club.

Green Reference (English Red only)

Midori, there is always something there to remind me!
The English Red has VRAM tile data on the title screen for "GREEN", which unsurprisingly cannot be seen in regular gameplay. The English Blue does not have any respective data for "RED", though.

Unused Japanese Text

Directly after text used for the names of the game's items, as well as the names of floors used for the elevators, there are some unused strings. While present in the Japanese Red and Green, they were not translated for the English Red and Blue, resulting in gibberish since the character table is incompatible between the two games. It starts from offset 4A92 in an English ROM, and is as follows:

Japanese name Translation Notes
かみなりバッヂ Thunder Badge The actual Thunder Badge is called オレンジバッジ aka "Orange Badge" in the Japanese version.
かいがらバッヂ Shell Badge All these "badge" strings are spelled with ヂ rather than ジ.
おじぞうバッヂ Jizo Badge -
はやぶさバッヂ Falcon Badge -
ひんやりバッヂ Cool Badge -
なかよしバッヂ Friendship Badge -
バラバッヂ Rose Badge -
ひのたまバッヂ Fireball Badge -
ゴールドバッヂ Gold Badge Same name as the Japanese version's Marsh Badge, except for the substitution of ヂ for ジ.
たまご Egg -
ひよこ Chick -
ブロンズ Bronze -
シルバー Silver -
ゴールド Gold -
プチキャプテン Little Captain -
キャプテン Captain -
プチマスタ Little Master -
マスター Master -

Unused PokéMart Data

PokéMart data is listed between the Fuchsia City and Cinnabar Island PokéMarts but doesn't seem to be used. It lists Great Ball, Hyper Potion, Super Potion, Full Heal, and Revive as available purchasable items.