Mutated Pokémon are different to regional variants in that they retain the original typing, but gain an additional type – their appearance changes a little in alignment with the new type. Mutated Pokémon are found in the same manner as shiny forms, in that they can be caught in the wild and bred – they just have very low encounter rates.
Let me know what you think, and if you have ideas for more.
by MDSM_art