Reposting from a different thread:
I've checked the event flags for anything to do with Mew, but I don't see anything explicitly set aside for it. There's also not one for Mewtwo, since that's also unavailable in the game. There are a lot of unmarked event flags though, maybe some of them are unused.
There IS an event marked for Zapdos, though, so you could add a Zapdos really simply to an area like the Power Plant.
>>31034301Here you go.
>>31034273You could also just add Snorlax and Carnivine to the wild.