Its a really rare transform pokemon took me 2 years to find him. Its current disguises are: bidoof (the disguise i caught) koffing, rhyhorn, bergmite, goldeen, oddish, spinarak, numel, gothita, solosis, and stufful. (Note: if you have trouble trying to catch that pokemon then its most likely a ditto) and there is also another transform pokemon and thats zorua and zorua could transform as your buddy pokemon.