The rarest possible instance in pokemon (via EnixLeDerp on reddit)
The rarest thing is probably encountering a horde of 5 shiny Spinda with identical spot patterns with perfect IV’s, same gender, a hidden ability, the same nature, and all with Pokerus, which is a 1 in 1.166516e+120 chance of happening.
To see that as a full number, that’s a 1 in 1,166,516,000,000,000,512,216,872,712,104,384,496,808,632,888,240,896,
040,352,200,480,240,248 chance of happening.
In words, thats a one in one novemtrigintillion, one hundred and sixty-six octotrigintillion, five hundred and sixteen septentrigintillion, five hundred and twelve tretrigintillion, two hundred and sixteen duotrigintillion, eight hundred and seventy-two untrigintillion, seven hundred and twelve trigintillion, one hundred and four novemvigintillion, three hundred and eighty-four octovigintillion, four hundred and ninety-six septenvigintillion, eight hundred and eight sexvigintillion, six hundred and thirty-two quinvigintillion, eight hundred and eighty-eight quattuorvigintillion, two hundred and forty trevigintillion, eight hundred and ninety-six duovigintillion, four hundred and eight unvigintillion, one hundred and seventy-six vigintillion, six hundred and forty-eight novemdecillion, four hundred and fifty-six octodecillion, one hundred and four septendecillion, one hundred and fifty-two sexdecillion, nine hundred and sixty quindecillion, seventy-two quattuordecillion, nine hundred and forty-four tredecillion, six hundred and forty duodecillion, eight hundred and eight undecillion, two hundred and sixty-four decillion, four hundred and fifty-six nonillion, five hundred and forty-four octillion, six hundred septillion, three hundred and ninety-two sextillion, sixty-four quintillion, forty quadrillion, three hundred and fifty-two trillion, two hundred billion, four hundred and eighty million, two hundred and forty thousand, two hundred and forty-eight chance of happening. You’re more likely to win the lottery one milion billion trillion quadrillion quintillion sextillion septillion times.
You’re more likely to guess what atom someone has chosen throughout all of the entire universe than this happening.