That's nice. I'm not sure how they got there, but hey, it's Pokemon. When the main method of getting rid of creatures you don't want is to hastily shove them into a computer in the game's equivalent of a truck stop, a few of them are bound to spill out in the shuffle. But then you notice that a lot of the old species that you caught just three years ago are nowhere to be found. Not just that, but they also seem to have been replaced by the new Johto beasts.
In the three years between Generations I and II, they were fucking wiped out.
It'd be nice to imagine that, even when dealing with a mass influx of an invasive species, the Pokemon World would organize itself pleasantly. None of the songs on my Pokemon 2.B.A. Master CD ever mentioned that the entire food chain in a region could be upturned when a fucking flock of Hoothoot move in. You'd think that they'd include a line about the rampant starvation that occurs when a population of Goldeen can't compete with Chinchou over limited resources in the "Pokerap," but they didn't. The "Pokerap" probably doesn't even rhyme anymore, because nature is a cruel mistress that will wipe you out the moment something evolves a tad faster than you do.