Nacho went from supine position to twisted... how can this be comfy?

Physics obeys them not the other way around!

For cats, laws of physics are merely suggestions.

Möbius loaf

Nacho looks like my Sushi, they could be siblings.

Their bones are literally not connected in the same ways ours are. Their spine is connected with muscles instead of ligaments, they have special spinal discs that let them flex further, they have a "floating" clavicle, etc.

they have extremely flexible spines compared to most other animals

My girlfriend often asks me the same thing