I'm talking about randomly finding one, not this saving before you get your starter/legendary and soft resetting thousands of times, or whatever that trick was in D/P/P where you could run into the same Pokemon multiple times and increase your chances greatly.
Again, I'm talkin' 'bout you're on your way to Sootopolis City and you run into a purple Wailmer.

Back in Silver, I was surfing for some reason (I think I could have just flown) and I ran into a Tentacool that for some reason I couldn't run away from, so I killed his ass. Later I find out that there's this thing called "shiny Pokemon" that are different colored, then I recalled that this Tentacool had green instead of red. After seeing that I was like "fuuuuckk..."

What's your story?