The idea of transplanting the human head has (so far) been left in the (fictitious) realm of the rich and crazy - see the incredibly strange 1971 horror movie
The Incredible 2-Headed Transplant or its apparent 'followup' the year after
The Thing with Two Heads or
The Simpsons: Treehouse of Horror II in 1991 - but now an Italian neuroscientist believes that it may actually be possible.
There have been stories over the years of scientists transplanting the heads of dogs and monkeys - btw, that's
between two dogs (by Vladimir Demikhov in the 1950s) and
between two monkeys (by R.J. White in the 1970s),
not between a dog and a monkey - with a fair amount of hype, but apparently, according to Steven Novella, from his
Neurologica Blog, those weren't true transplants. For it to be a true transplant, the head has to be able to control its new body, and in those cases, it was simply that the body supplied blood to the head. In order to have control over the new body, there has to be a successful connection of the spinal cord. Without that, it's no dice.
Now, in the fictitious examples I mentioned above, Manuel Cass (the 'maniacal killer' from
The Incredible 2-Headed Transplant) was an actual transplant, as he had some control over the body, but for Dr. Maxwell Kirshner in
The Thing with Two Heads and Mr. Burns in
Treehouse of Horror II, they were just grafted on.
However, although I've been using examples from horror movies and cartoons, there actually is some real promise for this idea, apparently.