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When shiny Mew/Ditto/Smeargle transforms, it transforms into a shiny version of the opponent's Pokémon (which is not what happens on retail).
Mew: https://replay.pokemonshowdown.com/gen71v1-754317117
Ditto: https://replay.pokemonshowdown.com/gen71v1-754319654
Smeargle...
Noivern's shiny sprites seemed a bit outdated, so I went ahead and updated them:
Current Sprites (for comparison):
Updated Sprites:
Also updated the front and back sprites for shiny Mega Glalie since in their current shiny sprites, only the eye color was changed
Current Sprites...