I read a series, I forget what it was, but the main characters were shapeshifters, and they could not ignore the conservation of mass/energy.
In this one, he's tried to shift into the form of a spider, to escape something I think, but he still had the same size and mass and it mess with his breathing and everything.
Oh, and they were addicted to basil.
Interesting take on it. The writer didn't try to handwave it by dramatically increasing density or anything? He was just a dude-sized spider?
My explanation was also partially to explain why he couldn't turn into a a Kaiju and just wreck everything; he
could if he had an adequate understanding of biology and physics and could actually design a creature that wouldn't immediately suffocate, collapse under its own weight, and had a circulatory system that functioned properly. I presume the limitations on Goodman Grey are similar in some regard, though I don't know if he could shift into something smaller than him, if he's importing matter from the Nevernever. Does he export it, too? And if he does, how does he get it
back?