Of course, rare Pokémon like Charizard and Dragonite would not have a chance of being a Ditto. Trainers might get upset if the rare Venusaur they thought they caught turned out to be a small pink blob. Niantic could even go the extra step and give Ditto the dot eyes and thin mouth that it retains after transforming in the anime. That way trainers would know they were getting a Ditto and could decide what items they wanted to use to catch it.
How do you think Ditto should be introduced into the game? Let us know in the comments below!