You may have seen this as an old thread, but one time my friend went to Giant Chasm, and in the first patch of grass he walked into he found a Shiny Metagross. He threw a plain old pokeball at it for the lulz, but the pokeball caught it on the first try. Upon checking it's profile, it had perfect IV's, pokerus, and an Adamant Nature. What are the odds of this sort of thing happening?
There is approximately a 1 in 93,061,505,980,825,600,000 chance of this happening. I got that somewhat quick so I may be wrong but that's what I got.