Wait... Dual Type Gym Leaders are ALREADY in Pokémon!?

A fun fan theory has been what it could be like if there were Gym Leaders that used more than one type in Pokémon, however what if I told you that this has already been happening for year...? We have in fact had Gym Leaders with teams that share multiple types, or simply used Pokémon that are outside their stated specialty, giving them that fabled second type! So let's go thru and see which Gyms and Elite Four members have in fact already been representing two types plainly for all of us to witness.