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Escape sprite handling glitch
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Miscellaneous glitches of Pokémon Red and Blue and Pokémon Yellow

Amazing Man (Red and Blue only)| Cable Club escape glitch | Celadon looping map trick | Champion Blue music muting glitch | Coastal Flooding | Cooltrainer move | Cycling based glitch maps | Escape sprite handling glitch | Evolve without an evolutionary stone (Red and Blue only) | Evolving Raichu (Red and Blue only) | Expanded item pack | Expanded Pokédex | Focus Energy glitch | Get stuck in a wall | Ghost Bicycle glitch | Glitch encounter system | Glitch City RAM Manipulation | Infinite Blaine Door | Introduction Nidorino glitch (Red and Blue only) | Invisible PCs (Red and Blue only) | Invisible tree glitch | Item stack duplication glitch | Mute the music in the Pokémon League | Partial trapping move link battle glitch | Pokémon Tower Pokédex glitch | PP Reset Glitch | Recovery move glitch | Rival's effect | See a Ghost without a Silph Scope | Selfdestruct and Substitute glitch | Silph Co. PC Glitch | Slot machine glitch | Stand on a tree | Statue behavior glitch (Red and Blue only) | Substitute glitch | Super effective move AI flaw (Red and Blue only) | Super Glitch | Surf down glitch | Swift miss glitch | Transform assumption glitch | Transform Empty Move Glitch | Trick Zone | Vending machine purchase glitch | Walk around with only fainted Pokémon (Red and Blue only) | Walking lag glitch | Walk on water through Surf | Walking Pikachu happiness glitch (Yellow only) | Wild appeared! | ZZAZZ Glitch

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The escape sprite handling glitch (coined by Pigdevil2010 as the Escape Rope sprite handling glitch) is a natural glitch in Pokémon Red, Green, Blue, and Yellow.

When the player uses Teleport, Escape Rope or Dig to escape from an area outside of Super Game Boy or Game Boy Color mode (however, a Game Boy Color or Game Boy Advance playing Pokémon Red and Blue is apparently fine), the player's sprite may temporarily be replaced with a flipped "ABCD" square in English versions, or a flipped "アイウエ" square in Japanese versions during the escape animation.

Escape sprite handling glitch JP.gif Escape sprite handling glitch EN.gif

Explanation

To display the Start menu, the game needs to load the tileset used for text, which overwrites half of the tileset used for overworld sprites. Specifically, the "walking" frames of sprites are overwritten. NPCs respond to this by reverting to the "standing" state whenever the tileset for text is loaded. The player sprite does not check the tileset, but normally it's impossible to open the Start menu (or display any sort of text) in the middle of a player step, so it's not a problem.

The problem comes from the code that handles the animation of the escape item. The player is supposed to first spin in place for a while, then start to move up while continuing spinning. For both parts of the animation, the function SpinPlayerSprite is used to change the facing of the player. That function assumes that the 4 byte list wFacingDirectionList has been initialized to some cyclic permutation of $00, $08, $04, $0C (down, left, up, right), with hl pointing into somewhere into the list. This is indeed the case for the first part of the animation.

However, for the second part of the animation, hl is erroneously left pointing to somewhere else, namely, wPlayerSpinWhileMovingUpOrDownAnimFrameDelay. This value is explicitly set to 2 on SGB, and 3 otherwise. Therefore, SpinPlayerSprite would futilely shift wFacingDirectionList around, while setting the player's facing byte to $02 or $03 depending on the platform.

("Facing values" that are not a multiple of 4 are used for the walking animation, which consists of 4 frames. For walking down, those are standing, walking, standing, walking and flipped (to "move the other foot"), corresponding to $00, $01, $02, $03 respectively.)

On SGB things seem fine, because $02 is just another name for $00 (facing down, standing), so the player just move off the top of screen without spinning. On other platforms, however, the facing byte is set to $03 (facing down, walking, flipped), but the corresponding tile has been overwritten, and hasn't been reloaded yet. Therefore the sprite is displayed as a flipped "ABCD" square.

The same programming error happens when the player arrives at the warp destination; however, by that time the tileset is already properly reloaded, so the player just drops to the ground in a walking posture (non-SGB platform) or standing posture (SGB) without spinning.

Youtube video

YouTube video by Pigdevil2010