Can we have your liver?

I was discussing some of the pros and cons and the controversies around cloning with my students the other day. Usually someone will make the comment about how it's not "natural" or how it would be nice to have a "spare" in case one of your organs fails. I take the one kids,usually a male, who makes the most noise about it in the class and say, "Okay, let's make a clone of you for spare parts. First we'll take some of your cells and remove the nucleus. Then we'll take several eggs from one of your female relatives. Your sister or mother or cousin. We'll remove the nuclei from those eggs and replace them with yours, for a full set of DNA. Then we'll put the refurbished eggs back in the woman and wait 40 weeks."
It's about then that they realize they have just made a baby. Puts a whole new spin on it. Having a baby with their mother or sister grosses several of them out, but the whole cousin thing doesn't seem to.
They have this idea that a clone would be a full size replica of themselves, likened to Hollywood Fiction. It really surprises them the science behind it.

Another reason we need a stronger push for science literacy in our country, but that's another post.

Then I tell them:

"Ok, one day your liver begins to fail. And you have to go to this person/clone and say to them, Uh, Can I have your liver? (In my head I'm John Cleese in a white coat, saying this in someones kitchen, with an English accent)."

Some students still don't get it, so I finish with:
"One day you parents sit you down and say, Sweety, we know you've been having a lot of fun, and actually think you have rights and expectations for a future. But, well, you're a clone of your mother/father (depending on their sex) and her/his liver is failing. So, uh, Can I have you liver? (again, with a certain Cleese-like lilt)

Gets 'em every time.