Niantic has been quite particular in how the expect Pokemon GO users to behave. In the Terms of Service for Pokemon GO, the company specifically states that data-mining tools and probing the game's code are against the rules and a good way to get your account cancelled, suspended or terminated.
However, that doesn't mean that people won't do it anyway. One user, who also happens to be a Reddit user, has data-mined Pokemon GO's code and found a couple interesting things. For starters, he found Ultra Balls and Master Balls, but that's not what the interesting findings are.
Of the 151 Pokemon in generation 1, Niantic only included 133 Pokemon, but this doesn't mean the rest of the Pokemon won't be coming to the game. The same data-miner found Ditto, Mew, Articuno, Zapdos and Moltres hidden away in the game's files.
These Pokemon will likely make an appearance during special in-game events, although it is possible that these Pokemon may not make an appearance in the game. These were simply files for the Pokemon that were found, that's it.
