Why does the weather forms of Castform have no shiny in old gens?

Question

I was looking at castforms sprites the other day and realised any form of castform that wasn’t the default form, never had a shiny! In fact the ‘shiny’ sprite was excactly the same as the original for multiple gens! I am really curious see castform’s sprites for reference here

Comments

Cus gamefreak didn't make em til later gens

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You mean if I got a shiny castform in… let’s say x and y if it changed form, no one would know if it was shiny?

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I’m just happy this question didn’t get closed like my last 2