>>37106026My headcanon is that there were a group of pikachu's that were used as 'lab rats' for the Aether foundation, so that they could be used to tamper with their DNA, for some weird study.
The pikachu that were tested upon, were given a unique genetic mutation that would change their appearance when they evolve.
These pikachu would be released in the wild later on and basically spread their mutated genes throughout Alola, hence why the Pikachu you catch in the tropical region would turn out to be a regional form of Raichu.
Also psychic=science so that would explain the connection as well.
