There's a lot of controversy whether Ditto is in the game or not, and whether he's been found. Well, let me tell you this, he's been found. The way to find Ditto sounds ridiculous at first, but it does make sense if you do your research.
Ditto is a pokemon that can take any shape it wants, even other pokemon. When players asked the developers how they could find Ditto, one of them responded with "always spin". I tried this myself, and have been spinning all the pokemon I catch, just in case they're Ditto in disguise. So far I only know one person that this has worked with, and I'm pretty sure nobody has figured this out yet.
Let me know if you catch a Ditto trying this, because I'm trying to catch one myself.