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The first shiny I ever encountered was in Leaf Green. I had heard of shinies but I had never seen one. One day I was in the battle tower and one of the AI sent out a shiny Espeon. I couldn't believe an AI had a shiny, and I was furious that I couldn't catch it.
Years later I catch a shiny...
Ever since soul silver I've loved Ampharos. It was always a reliable member of team as well as being adorable. I remember I'd go to the top of the light house just so it could visit the Ampharos you helped as part of the story.