On my old Yellow version save file – the one I loved, the one I started shortly after beating the game for the first time when I was ten years old because I didn't know you could just continue after beating the Champion – I had a glitched Jolteon.
Specifically, when you tried to view his stats, the screen would just go blank. It really freaked me out the first time it happened; I thought the game had crashed somehow. But when I pressed A after that, the stats did appear – only some of what was meant to be on the status screen was missing. (In particular I remember vividly that the IDNo/ and OT/ labels were missing.) The second status page was perfectly normal. This happened consistently, exactly like this, every time I viewed this one Pokémon's stats. There was nothing wrong with any other Pokémon I had, or anything else in the game, and in every other respect he was just a normal Jolteon. But he was glitched, so he was different, so he was awesome.
Jolteon hadn't been one of my original team members on that save file. But after beating the Champion (by this time I knew I could continue afterwards), I had set about training up other Pokémon off my PC, both to complete my Pokédex and just for fun, and one day I took out my Eevee, the one I'd gotten from Celadon Mansion during my playthrough. I'm pretty sure I discovered the glitch the first time I viewed his stats after withdrawing him. I remember being torn about evolving him; I had the thought that maybe evolving him would fix him, reset whatever was going on, and while on the one hand I didn't want this weird glitch to mess up my game somehow, on the other hand this was something weird and unique and kind of cool. But as luck would have it, he stayed exactly as glitched after I’d used the Thunderstone. If not for the glitch, I would probably have just put him back on the PC after training him up to catch up with my team at the time, like all the other Pokémon around that time that I trained to high levels just because I felt like it. But as it was, Jolteon was special, so I just had to keep him on, even though having a second Electric-type alongside my Pikachu was kind of redundant. He became a permanent team member, and I showed him off to anyone who would care (mostly my cousins).
I never knew why my Jolteon was glitched. It was a genuine cartridge, bought new, and I'd never used a cheating device or exploited glitches of any kind. (One time, I'd attempted to perform the classic Old Man Missingno. trick after reading about it online – but of course it hadn't worked, much to my disappointment, because I was playing Yellow, which had fixed that particular glitch.) At the time, I only had the vaguest idea of a "glitch" as being when something just randomly happened wrong on the game; I didn't question what was actually going on here that was making this consistently happen for this one Jolteon, and I didn't have the knowledge or mental capacity to properly assess exactly how weird it was. For all I knew, maybe this just happened sometimes.
In 2003, when I was thirteen, I let a visiting cousin from Denmark play my Yellow version for a bit, and she started a new game and saved. (It wasn't really her fault – she had little reason to know that an innocuous-looking menu option in an unfamiliar game would just delete my own progress with little warning, and I sort of realized that but didn't know how to communicate that to her with my limited Danish.) I was absolutely devastated – for all the hundreds upon hundreds of hours I'd sunk into it, completing my Pokédex and training up so many Pokémon, but mostly because I was very emotionally attached to my team: the Pikachu that I'd trained to level 100 (I'd done it in a frantic, desperate bid to make him happy again after I'd deposited him on the PC once to try a dumb rumour about how you could get into Bill's secret garden if you had six specific Pokémon in your party), the Charizard that had made me love Charizard, Blastoise, Pidgeot, Dragonite – and, of course, my glitched Jolteon. When it happened, I'd been in the process of training up the rest of the team to level 100 through repeated rounds through the Elite Four, but they never made it there. In the intense way that only kids can feel, it was like losing friends.
After a while, I started a new file and tried my best to recreate my old save: I named myself TRAINER (something I'd done when I was ten because it felt more official, somehow), I caught the same Pokémon, I put together the same team as before. I got Eevee from the Celadon Mansion with bated breath: maybe some sort of production error on my cartridge meant that the Celadon Eevee would always have the same glitch? But no: my new Eevee was just a normal Eevee. In a very definitive, tangible way, it would never be the same.
Back then, I mainly just grieved my lost partner. The glitch only mattered because it had made him special. But years later, by the time I had a degree in computer science and had personally dug into some of the games' programming, my thoughts began to wander back to my Jolteon. Glitches in video games aren't just something being weird at random by magic: there had to be a concrete explanation for what was happening there. And yet, in all those years since, as fans discovered and documented everything from exactly why Missingno. has the stats it does to ways to completely break the game and make it blissfully execute arbitrary code, I had never, ever seen another person describe the same glitch that had happened with my Jolteon or anything like it. I knew it was real – it wasn't something that'd happened once that I could have been dreaming or imagining, but something that had happened consistently, every time – but now I didn't have that save anymore to verify it, or even so much as a video of it (video recording devices weren't anywhere near as ubiquitous back in the early 2000s as they are today).
...And, eventually, using an emulator and modern tools, I did successfully manage to replicate the glitch! What was wrong with my Jolteon turned out to be that a single particular bit in his original trainer name had somehow gotten flipped from zero to one - probably by a cosmic ray. This changed the final "end of string" character at the end of the name into a "paragraph" character - the delimeter the game uses to signify the end of one box of dialogue and beginning of the next. When the game encounters this character, it will stop and wait for a button press and then clear out the portion of the screen corresponding to where the dialogue textbox is on the screen; thanks to the order in which the status screen is rendered, this causes it to wait for a button press before showing anything, and then when you do press the button, the labels and the OT name itself get wiped out before it continues to render the rest of it. (If you'd like to read more about the details, the article on my website gets into the weeds of how it works and how I discovered it.)
There's a big sense of catharsis in having finally solved the mystery of my Jolteon - and it feels like an appropriate way to honor his memory.
Goodbye, Jolteon. You were very, very special.
