|Please note that this glitch only exists in the Spanish version of the game.|
Map 0xFF is a special map handler and glitch map.
Map 0xFF seemingly cannot be accessed by editing D369 (exit destination) to 0xFF or D362 (map number) to 0xFF while walking through a door, as both seem to always result in a white freeze.
For unknown reasons, it can be forced as a glitch map that does not freeze the game through a warp in map 0x0B, if the data for the map's script pointer (initially $CC5B in WRAM) is safe.
This glitch map appears with a glitchy tileset made up of people tiles with map block data sourced from $02D1.
In this glitch map, glitch music plays with the low HP beeping noise, and Pikachu can be seen gradually moving down the screen.
The map script for this glitch location is pointer $1A04. If the map script location is left at this address, later the palette becomes tinted white, Pikachu disappears and Red's sprite will show but there will be a glitch message box that plays some sounds for a while before possibly freezing the game with an invalid opcode or a white screen otherwise.
If the map script is forced to a harmless pointer with only ret (0xC9), the map may instead warp the player to Team Rocket Hideout (0xC7) valid source map Glitch City.
Pikachu moving down the screen.
The Team Rocket Hideout Glitch City.