"I battled a Mew and it deleted my save file" almost sounds like a creepypasta and yet, it is completely real. Welcome to the wild world of Pokémon Red and Blue glitches, where terrifying corruptions are possible.
For years now, hardcore players have known about the "Cooltrainer" glitch, an exploit that is "meant to represent the empty spaces in the movelist of a Pokémon that has three or fewer moves," according to Bulbapedia. By forcing the game to believe that this blank move was the first in a Pokemon's move list, the game can become corrupted. Using the blank under certain circumstances can have random destructive affects according to Bulbapedia.
YouTuber Crystal_ took this glitch up a notch by bringing it into a link battle. Fun fact: an opponent's player data is actually just a copy of your own info, at least as far as your Game Boy is concerned. So if you corrupt your own data, you can wreck havoc on someone else's game with some know-how, as the video below explains:
The thing about Red and Blue is, they're glitchy as hell. Players have figured out that they can manipulate a game's memory, such that they can alter the in-game rules on the fly using something called "arbitrary code execution" (ACE). In this case, Crystal_ uses a Cooltrainer-related ACE to tell the opponent's game to delete its own save file, with some added flourishes such as a glitch monster.
Pretty wild, huh? The danger is that, if done incorrectly, the player risks deleting their own save file. Imagine pulling this off against someone else when you were a kid! It would have been legendary (and very dickish.)
Pokémon fans have been on a roll with ACE-related shenanigans in 2017. Last month, MrCheeze figured out how to use a Red/Blue save file to bring Cosmog "into" Pokémon Stadium -- an N64 game.
"The effects are triggered by glitching the save file of a Game Boy game in the Transfer Pak, so that there are more than 20 Pokemon in the last PC box," MrCheeze wrote on the YouTube description. "This causes a buffer overflow in Stadium's trade system." It is the first exploit of its kind.
"Up until now though, just about all the known ACE exploits (or at least, those achievable through gameplay) have been for 2D systems," MrCheeze said. "The NES, SNES, Game Boy, and GBA all have such exploits, but up until now the N64 has evaded everyone's attempts to crack it. Part of the reason for this is that the N64 is programmed in C, rather than everything being written by hand in assembly - which doesn't eliminate the sort of severe bug that allows us to run arbitrary code, but definitely makes them a lot rarer.
But with a third dimension opened up, I'm very interested in seeing what people can pull off with this. The traditional Doom port that every system has to have? An exact recreation of Super Mario 64, except where jumping doesn't require you to press the A button? There's really no limits, except those of the N64 hardware itself."