Because it sounds insane (and is also actually insane), no one's ever seriously considered ... ha ha, I'm just kidding. Of course someone's done this. On monkeys, at least. In the 1970s, Dr. Robert White did exactly this with a living monkey and some spare monkey parts. It worked, sort of. The poor fucking thing managed to survive for a few minutes. One observer described its facial expressions as looking "like terrible pain and confusion and anxiety."
Well no shit.
And because this ludicrous example of monkey torture was so obviously insane, it was never attempted again, and-- oh wait, no. Look, here's a Chinese surgeon who's done the same thing thousands of times to mice. There are pictures in that linked article, in case you're curious -- which I'd encourage you not to be.
AndraA Cerar/iStock/Getty Images
Here's one of a mouse humping a mouse instead.
And good news! At least one Italian doctor has plans to do this on a real man. In that particular case, the patient in question has a degenerative disease, so I guess it's only partially horrifying. Still, it seems a little reckless to waste an entire body, full of organs that could save many people, on a plot from a Scooby-Doo cartoon. Maybe let's just all cool it on the head transplants for a while, OK?