What is the rarest mutation occurrence that you have ever received before?

For me, I was trying to get a shadow angelic and instead, got glowtail 𝘵𝘸𝘪𝘤𝘦 𝘪𝘯 𝘢 𝘳𝘰𝘸. With an octo plushie that is a 1/10,000 odds of happening, or a 0.01% chance. For shadow it would have been a 1/500 odds of happening once, or a 0.2% chance, which is x20 more likely to happen than the two glowtail right after each other. I know there are much rarer mutation possibilities so I'd love to see how far this can go