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Jigglypuff mistakenly ended up with two completely different eye colors: green and blue. While it was always meant to have blue eyes, the initial anime promo art depicted it as a weird fuchsia color with green eyes. A LOT of merchandise (like pic related) decided to go with that color scheme. When Jigglypuff eventually debuted in the anime, it had its normal blue eyes, but were later changed to a green-ish color the match the incorrect promo art. Gamefreak later complicated matters more by giving shiny Jigglypuff green eyes.
