Assuming you look at only 2 wild Spindas from Ten Carat Hill and don't use anything to influence chances, the first Spinda has a 2^-12 (aka 1/4096) chance of being shiny. The second one has another 2^-12 chance. source I think Spinda's spots are determined by a 32 bit number, so the second Spinda has a 2^-32 chance of having the same spots as the first. source The second Spinda has a 1/25 chance of having the same nature as the first. source Wild Spindas can be between levels 10 and 13, so the second Spinda has a 2^-2 chance of having the same level as the first. source The second Spinda has a 1/2 chance of having the same gender as the first. source The chance that all of these happen at once is the product of all the chances, which is 2^(-12-12-32-2-1)/25, which is close to 1/1.44115188E19.
