he, they
Seen February 23rd, 2023
Posted February 22nd, 2023
There's fundamentally not much of a difference between a shiny and just any other Pokémon of alternate color (from an in-world, faux-biological standpoint).
They're both mutations (and non hereditary mutations at that) but I guess shinies are consistent in a way that just randomly having a different color wouldn't be.
I wouldn't say it was the first shiny so much as it was the first shiny to be widely seen and broadcasted. The out-of-world explanation is that they wanted GF to draw attention to their shiny (ba dumm tss) new mechanic and worked it into the story, but since you can get shinies before the Red Gyarados event they were presumably always there, you just never lucked into one in Gen I / people didn't really see them before.
Like Pokémon eggs - presumably Pokémon always bred using eggs before Mr. Pokémon / the Daycare Couple saw one, humans just didn't really see the eggs.