I actually confuse the original region of most of the Pokémon appearing in the sixth and seventh generation.
Sometimes I think of Comfey as a Kalos Pokémon, Goodra as an Alola 'mon, Turtonator as a sixth generation Digimon, etc...
I always find myself thinking that Mimikyu was introduced in generation 6 as opposed to generation 7 and is thus native to the Kalos region. Similarly, Hawlucha is a Pokémon that I continually associate more with generation 7 than generation 6. I have a tendency to confuse both gen 6 and 7 Pokémon in general.