Map hex:99 house door glitch

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The map 0x99 house door glitch occurs in Pokémon Yellow.

It involves the player warping to map 0x99 (a house in Fuchsia City with NPCs discussing Bill) and not being able to use the exit, until walking at least one step.

Requirements

• A means to warp to Map 0xFE, such as via adjusting the quantity of item 36 in the expanded item pack to 254.
• The map script for map 0xFE (stored at DC0E) must be safe. Having a Pokémon with exactly 201 or between 51456-51711 experience in the 12th slot of the current storage box is usually enough, because it will force the game to encounter the ASM instruction "ret".

Steps

• Warp to map 0xFE. Shortly afterwards, you should immediately automatically warp to map 0x99. Now try to go down. Much like Mr. Fuji's house door glitch, you won't be able to exit the house until you make at least one step on another tile.

Note that warping to map 0xFE will cause heavy glitch meta-map script activation. Many maps in Kanto will now freeze the game, with no full fix without arbitrary code execution or erasing the save file, so it is highly recommended not to save after visiting map 0xFE. Powering off or resetting the game after visiting map 0xFE without saving is fine however.