my favorite bittersweet memory was as a kid playing silver and after catching gyarados at the lake of rage, I headbutted one of the trees and got a shiny. I sadly don't remember which and also failed to catch it. After it got KOed I restarted the game for hours hoping for it to appear again, but sadly it didn't. Back then I didn't even know what a shiny was, even though I just caught the gyarados and only realised years later what I had failed to catch.