Back in the days of Ruby and Sapphire, I had just beaten it a few days prior to this. I was fishing around Mossdeep for a Sharpedo with my Super Rod, and I kept finding Wailmer after Wailmer with the occasional Carvahna (spelling?) and Tentacool. After a while of searching, I came across a purple Wailmer, and stars appeared when it was shown. I had heard of Shiny Pokemon before, but I never actually had the chance to encounter one. So I raked it up in a Net Ball and was really happy. So happy I forgot about my Sharpedo. I evolved it into Wailord and it was a total bro. Later on I transferred it to my Pearl, only to later be lost after a tragic mistake my 12 year old brain made. I had just gotten an action replay and had put in a special code that would give me a Shiny Wonder Guard Spiritomb, and since I didn't have a Spiritomb atm, it was worth a shot. After I had the Spiritomb for a while, my PokeRadar showed that I had an egg waiting for me at the Daycare, and the only Pokemon I had there was my Ditto. So I took the Egg and (my 12 year old brain decided this) hatched it into a GLORIOUS MissingNo. It was at the front of my party, so whenever I was in battle I had to send it out, because the PC read it as though something was there but wouldn't let me pick it up, and I couldn't switch it around. Finally I decided to start trading my Pokes over to my cousins Diamond five at a time. This was taking WAAAAY too long, so before I got to my Shiny Wailord, I decided to clear the data and start anew. It wasn't until later did I discover my Wailord had been erased. I was so angry. Now, six years later, I have recreated that Wailord on my PokeCreator app, but it just isn't the same.
Moral of the story: Don't hatch Bad Eggs, people.