>>48927547Not that anon, but
Whenever you enter a tile of grass, the game reads data from that tile and sets the Wild Encounter table.
The Missingno glitch works because when you do the "Old Man catches a Weedle" tutorial, the game stores your name somewhere in memory, changes it to Old Man for the duration of the battle, then changes it back when the battle is over.
The chunk of memory where your name is stored is the same location where the Wild Encounter table is normally held (or at the very least it overlaps with it). Computers have so much memory nowadays that no one bothers with this level of optimisation any more, unless it's for an operation that will be repeated on a massive scale where even small improvements add up.
The column of surfable tiles on the eastern coast of Cinnabar Island has wild encounters enabled, but the devs forgot to give it any Wild Encounter Table, so it just uses whatever was last loaded. This means that if you load your name into the Encounter Table slot, and don't enter any other grass to overwrite it, it will interpret the bytes of your name as if they were an encounter table, even if this would result in impossible things like "Pokémon #247 at Lv.105".
There are only 151 Pokémon in the game. Let's say a single Pokémon is 8 bytes. In that case if you try to load Pokémon #153 then it will grab whatever data is 16-24 bytes after Mew. The first few of these are leftover unused Pokémon slots with the name Missingno. ("Missing Number") attached, but if you go far enough then you'll hit the bytes for things like map tiles or program logic which were never intended to be read as a Pokémon.
