I found this tweet which I replied to at the time:
Although it involved battle RNG manipulation as Anubis explained, they outlined the chances of everything happening:
- 1 in 8912 (assuming this was a shiny encounter without Shiny Charm or any form of chaining)
- 1 in 636 to get Sing
- 11 in 20 for Sing to land
- About 3 in 10 to get all 3 sleep turns
- 1 in 636 to get Guillotine
- 3 in 10 for Guillotine to hit
- 1 in 10 for Focus Band to leave the opposing Pokémon on 1HP
- Critical capture chance unknown
That’s ropey maths but chaining them altogether, you about 0.000000000147539%. The most difficult lotto jackpot to win is the Italian SuperEnalotto jackpot which is 1 in 622,614,630 or 0.000000160612994%.
If any of those calculations are off, let me know in the comments, please don’t judge, and I’ll correct it.