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Viridian Forest 0xF8FF glitch
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Major glitches of the Pokémon series

Arbitrary code execution (template, remote, cart-swap, unintended ROM code execution) | 2x2 block encounter glitches (Left-facing shore tile glitch (in-game trade shore encounter trick, old man trick, Trade link up shore encounter trick, Fight Safari Zone Pokémon trick)) | 99 item stack glitch | Bad clone glitch (????? party overloading (Type 0xD0 move glitch, ????? map corruption, | Celebi trick, Celebi Egg trick, Shiny Celebi trick, glitch move map corruption, overloaded party map corruption, Glitch Unown (Glitch Unown map corruption) Duplicate key items glitch (infinite items and item creation, expanded Balls pocket (TM/HMs outside of the TM/HM pocket, Glitch Pokédex categories)) | Berry glitch | Bug-Catching Contest data copy glitch (Japan only) | Cloning | Ditto DV manipulation | Elite Four door glitch (Japan only) | Expanded party encounter table manipulation | Glitch City (Safari Zone exit glitch, RAM manipulation) | Glitch meta-map script activation (Generation I) | Infinite Master Balls (Colosseum) | Large storage box byte shift glitch (storage box remaining HP glitch, maximum stat glitch) | Item duplication glitch | Item stack duplication glitch (Generation I expanded items pack (Glitch Rocket HQ maps, Map FE (English and non-English European Yellow), Map script pointer manipulation (arbitrary code execution, map script pointer item ball manipulation), Text pointer manipulation (arbitrary code execution, item ball manipulation, mart buffer overflow), Trainerless instant encounter glitch) | Transform held item glitch (Japan only) | Mimic glitch (Japan only) | Out of bounds Glitch City (Generation II) (Slowpoke Well out of bounds corruption (French version)) Lumiose City save glitch | Pikachu off-screen glitch (Trainer corruption glitch) | Pokémon merge glitch | Pomeg glitch (Pomeg data corruption glitch) | Roaming Pokémon encounter glitch | (Mimic) Transform Rage glitch | Select glitches (Japan only) (Closed menu: Dokokashira door glitch (international), Fossil conversion glitch (international), Second type glitch, Skip to Level 100 glitch, Trainer mutation glitch, walk through walls (international) Special menu: Lift glitch, Badge describer glitch) | Sketch glitch | SRAM glitch (Generation I) (255 Pokémon glitch, send party Pokémon to a new game) | Surf down glitch (Grass/rock Surfing glitch (Spanish/Italian only) (English)) | Time Capsule exploit | SRAM glitches (Generation II) (Mailbox glitches, Mystery Gift item corruption, Trainer House glitches) | Tweaking | Trainer escape glitch (Death-warp, Mew Trick, Ditto Trick, Experience underflow glitch) | Buffer overflow techniques (Japanese unterminated name glitch item instant encounter glitch, LOL glitch, Rival LOL glitch, Instant LOL glitch, RAM LOL glitch, oobLG, blockoobLG, Instant encounter infinite chain glitch (LGFly)), Super Glitch (Generation I) (party remaining HP glitch), Super Glitch (Generation III), Text pointer manipulation mart buffer overflow glitch, CoolTrainer♀-type move, Double distort CoolTrainer♀ corruption, Yami Shop glitch) | Walk through walls (ledge method, museum guy method, Rival's effect, Select glitch method (international), Brock Through Walls) | ZZAZZ glitch (party Pokémon box data shift glitch)

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The 0xF8FF glitch activating a Hall of Fame warp from Viridian Forest

The Viridian Forest 0xF8FF glitch is a major glitch in Pokémon Red and Blue which involves arbitrary code execution of the 0xF8FF region Echo RAM in Viridian Forest, due to a special glitch meta-map script activation. It was documented by gifvex.

This glitch may not work on certain emulators due to its abuse of specific CPU timing.

Although this location within the opponent Trainer's Pokémon data is tricky to manipulate, it can be made to run the Hall of Fame script. However, in order to run the Hall of Fame script a specific Trainer ID, player name, stored Pokémon data and some luck is involved. This includes having a 'good' current play time specific up to how many frames have passed before the next second.

This glitch is currently the fastest means of completing English Pokémon Red and Blue other than the SRAM glitch, obsoleting Brock Through Walls for this purpose.

Steps

First name your player mMna.♀tF (the name is important) and manipulate the Trainer ID 61896 (F1C8), also important. Choose Charmander or Bulbasaur as the starter. It will get the ID 61896 which is necessary for the run.

Note: A different player name and Trainer ID have been used for TAS purposes, but these haven't been examined for non-TAS use yet.

Now continue the game as normal until you get to Viridian City, in which you should find a Spearow on Route 22 and name it "AAA". Then deposit your starter into the PC and use the 'death-warp' technique to blackout on the last Bug Catcher.

This means getting an encounter in the grass in the Bug Catcher's vision and fainting. This causes you to black out but sets up an instant encounter when you return. If using luck manipulation you can encounter a Pikachu to faint Spearow, otherwise poison Spearow beforehand.

Now, don't open the start menu or open any text boxes (or the glitch won't work properly) and return to Viridian Forest. You will re-fight the Bug Catcher. Win or lose against him, then you will immediately battle him again (again you can win or lose this fight). This activates glitch meta-map script 06, which causes lag when you walk and can interrupt A button presses.

Next save the game south outside of Viridian Forest to be safe, as your play time (including frames) can affect the upcoming Hall of Fame warp. Proceed to the first Bug Catcher you can fight and mash A until you get his encounter text to appear.

Win the fight and if lucky, you will enter the Hall of Fame.

If you want to do this with no luck manipulation, obtain the ID 61896 by swapping a quantity of 241 into item 30 and a HM05 into item 31 (see expanded items pack), then obtain a Charmander at Level 6 from the Trainer escape glitch and trade it over to the new game to deposit it into the PC.

You will still have to be lucky to encounter Spearow, get the death-warp and get Hall of Fame to work however.

Technical information

For instant encounters from Trainer battles the game uses something called 'meta-map scripts'. These are scripts for a number of maps to perform a task (such as to encounter the Trainer, to stop the player from leaving Pallet Town into Route 1 and so on).

Due to a glitch beating the Trainer two times sets the meta-map script to glitch value 06. This causes walking lag. Proceeding to beat the other Trainer will execute F8FF in Echo RAM (in the middle of enemy Pokémon 3's data), in which copies of the player's name are executed as code. The code falls through to play time (in which the values including frames need to be 'safe'), and then to the stored Pokémon's data.

Here if we have exactly 1 specific Pokémon with the right ID you can proceed to execute the Hall of Fame script.

TheZZAZZGlitch also did further research into this. Apparently the execution of F8FF is due to an invalid predefined command function 0xF4. Apparently the code is supposed to execute F808 but ends up executing F8FF due to a VRAM inaccessibility related detail.

This glitch may not work on VisualBoyAdvance, Pokémon Stadium 2 or possibly Nintendo 3DS Virtual Console.

Credits

  • Gifvex (documentation)
  • ChickasaurusGL (article/video description, information)

YouTube video

YouTube video by ChickasaurusGL
YouTube video by gifvex (via TASVideosChannel)