There's this picture I saw on Inkbunny once. It wasn't necessarily well-drawn, but the concept behind it was fascinating.
There was this creature, I didn't notice the gender, and they were able to stretch their anus so absurdly wide that they could wrap the rectal walls over their head and effectively turn themselves inside out. Or maybe they just had a massive prolapse? I don't know what exactly happened to them, but they looked like a mirror universe burrito when they were done.
It's not that I am turned on by the idea, which I'm not sure if I am, but a feat as ridiculous as that needs to be preserved for posterity. You never know, someone might think they were the first person to come up with this idea, and we wouldn't want that.