I am a little confused with the story. At first Crowley said that he couldn't take the damaged kidney from Caleb because if he harvested the healthy one, he would die.

But then he put it into Joe and said that the knife just missed hitting the kidney. So which is it? Does Joe have a now-damaged kidney inside of him (karma) or is it a healthy kidney?

I love the idea of them getting caught and the kidney given back to Caleb, but I don't know whether Joe's antibodies would have damaged it to the point where it would be harder for Caleb to get it back without anti-rejection drugs.

If they can't re-harvest it, I'm hoping that there is a rejection and Joe loses the kidney and sepsis then takes over.

I loved the fanfic that Joe takes Steph's kidney, thinking her to be Caleb's daughter, and then he dies.