I've played enough Pokemon to get my fair share of random encounter shinies (and I've used nearly every shiny-hunting method known to man to get way more than my fair share) but I have two shiny stories that are crazy enough to be worth telling. Oddly enough they both come from my cartridge of Pokemon Diamond.
Now, Diamond was only my third Pokemon game after Fire Red and Emerald. When I started, I knew a little bit about shinies from the anime and from seeing a shiny Pidgey on my brother's Leaf Green file. However, I had not yet experienced the glory of a Johto game. So, when 11-year old me first saw the opening scene about the Red Gyarados search in Lake Verity, I didn't realize that it was just a reference. For the first ten minutes of gameplay, I was hopeful and excited for my chance to catch the crimson monster. But after starting the real adventure without any further mention of the lake exploration, all thoughts of Red Gyarados were quickly replaced by the sheer joy of destroying things with my Piplup.
Fast forward, and after a couple weeks of gameplay, I am at Lake Verity (I thought I remembered that this happened during normal gameplay, but I guess it must have happened during post game because that's when you get the Super Rod. I'm not sure why I was at the Lake during Post game, though). All I remember is that my very first encounter in the lake was a genuine Shiny Gyarados.
After recovering from my initial awe, I realized two things:
1. It's a Red Gyarados in Lake Verity, exactly like they mentioned in the beginning of the game, so it's obviously part of normal gameplay that I encounter and catch it.
2. I had forgotten to stock up on Pokeballs.
Now I had the master ball at this point in the game, but my Gen III experience told me that I should save it for a later roaming legendary and not use it on a Pokemon that can't run away. So, I just used my normal tactic for catching static legends and lowered its health as much as possible before chucking my handful of remaining Ultra Balls on it. The Gyarados seemed to mock me by breaking out of all of my balls, the shower of stars each time rubbed more salt in my wounds. Even after using my last Ultra Ball, I didn't want to use the Master Ball because I was certain that the Gyarados would still be there if I reset the game. So I turned off the game, my only regret being that I would have to replay the hour or so of gameplay since I had last saved.
You can probably figure out what happened next. 11 year-old me quickly replayed the game up to that point. I bought all of the Ultra Balls I could carry and excitedly made my way to Lake Verity. I tried for hours trying to find the Red Gyarados again. Did it only appear on certain tiles? Did I have to do something else to unlock it that I had missed this time? Was it not guaranteed, but just more common than usual? Eventually, I gave up trying to find it on that playthrough. But for every playthrough over the next 5 years, I spent a considerable amount of time trying to find it again before I actually used the internet and learned that the game intro was all lies and I had blown a 1/8192 chance.
Next story:
About a year after finishing my first playthrough of Diamond, I had done everything worth doing in Sinnoh and wanted to try the main story again. However, I had transferred all of my Gen III Pokemon to Diamond, and didn't want to erase their data. I didn't have a second DS or anyone to trade with at the time, so I started a new game without deleting my old data. Through prior experimentation I knew that this would keep all of my old Pokemon intact, with the catch that I wouldn't be able to save anything from the new file. I was fine with that because I only wanted a new adventure, and figured I would just leave the DS on and plugged in for a couple of weeks so that the game wouldn't turn off while I finished the main storyline.
I wanted to use 6 Pokemon that I hadn't before, so I chose Chimchar as a starter and caught a Starly on the first route. I had just gotten the bird on par with Chinchar's level when I encountered another Starly, a brown one that emitted blue stars. I managed to catch the shiny this time, and was quite upset that it happened on a file that I couldn't keep. I decided that I would make the most of the opportunity by not catching any other Pokemon and just keeping Starly and Chimchar in the spotlight. My shiny bird and little monkey quickly grew into two super sweepers that took Sinnoh by storm and perfectly matched 12-year old me's preferred strategy of hyper offense. By the time I got to Cynthia, I was so attached to Staraptor and Infernape that I would have traded all of my old data to keep them alive. I tried to save the game, but it wouldn't let me because of the unerased older file. After the championship battle, I said goodbye to my blue bird and finally turned off the game.
Since then I have played Soul Silver and abused Diamond's Pokeradar enough that I have multiple Red Gyarados and Blue Staraptors. Despite not being able to keep my original versions of these Pokemon, they are some of my all-time favorite shiny forms. To this day, l get unreasonably annoyed when I watch the intro to Pokemon Diamond, and unreasonably happy when I see a shiny Staraptor take the field.