This was a sub-plot in the Tank Girl movie. Half-man/half-kangaroo. I think Boogah said he was a dog before upgrading to human.
I still like that movie!
A little dated, but fun.
So, I've been thinking of it. If they make human parts for transplant by using an animal source, if they can grow the organ in such a way that the animal is not restrained, but free range. Like a free range cow, with a bulge on its side under the skin, where a human kidney is growing, i'd be ok with that.
They do a local anesthetic, cut open pouch. Remove human kidney, suture up veins, let pouch dwindle down. Give cow a year to recover.