First he is every single Pokemon in one, Second you could beat every gym leader by turning him into each Pokemon´s nightmare but he needs to see a Pokemon to turn into him but with enough patience you can teach him how every single Pokemon looks like and make him remember all of them, Fourth he can pretend to be you to go to places you don´t wanna go, Fifth since he his every single Pokemon in one you can get 6 Dittos and have 6 of each Pokemon and be invinsible, And last with the abillities of each Pokemon he can help you on almost anything for example:make your crush fall in love with you by turning into Luvdisk, Help you with litteraly anything with Alakazams IQ, Heal you with Chansey powers and so much more. Gotta say that Mew can also learn this abillity but he needs time so Ditto is the best Pokemon Ever!!!!!!!!!!!! and he can turn into shiny Pokemons so screw Shiny Hunts get yourself a Ditto!