This has been bothering me for a while now. Ditto? Ditti? Dittos? I call them Dittos but I’m probably pronouncing it wrong. If you answer this question, please include a link to where you found your info. Also, don’t ask why I need to know this, because I don’t really have an answer for you lol.
The correct plural form for all Pokémon names is no different from the singular form. So the correct plural form of ‘Ditto’ is actually ‘Ditto’. You might say, ‘Yesterday I caught multiple Ditto.’
Though it’s generally convention in English that plural nouns take an -s or -es suffix, there are multiple exceptions — for example, you don’t say ‘sheeps’. In the case of Pokémon, it’s probably just convenient to avoid making a separate rule for every species.
For example, the game itself does not add suffixes or alter spelling when hordes of Pokémon appear.