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Hey OP, did you know that Missingno exists because of a quirk in the sprites? Each tile is comprised of four "subtiles", and RB checks the lower-right subtile to see if an encounter is possible, and if it is it pulls from the encounter table found in the lower-left subtile. If it's not a water subtile then it pulls from the area's grass table instead, which if not loaded is whatever was written there last, since Cinnabar Island and the Seafoam Islands don't have grass encounter tables. Badly called index entries causes the game to call for an unknown Pokemon, and the sprite data for said Pokemon is taken from a specific memory location, calling and displaying bad data. Because of this you will NEVER encounter Pokemon while surfing on the Northern coast of Cinnabar Island, but you can encounter normal seafaring Water-types when surfing on the Southern coast.
