>>35046312This. I’ve said this here a few times.
When we saw Sun and Moon were gonna tell if a move was super effective during battle, I thought that was because Jigglypuff and other previous non-Fairy Type gen 1s were gonna have their original typings when transferred from the VC Red, Blue and Yellow, and this was to help differentiate.
That idea, coupled with Alolan forms being announced lead me to believe that Gen 1 designs that changed over time would be considered Kanto forms when transferred from the VC to SM and fat Pikachu would be one of the ones you could have.