"Sick of your life? Ready for a change? Sell off your unnecessary body and become a neurodonor! Dogs don't have worries, why should you?"
"Neurdonors" is the collective name for anyone who donates their body, but retains their central nervous system. Their CNS is placed into the robotic body of an animal, anything with four legs really. Dragons, centaurs, and pegasi aren't possible because the brain power required to power six limbs is beyond human concentration.
AEU Neurodonors Edit
There are, of course, exceptions to everything. In order to run a body with six limbs, you need to have an AEU implanted in your brain. This is what allows Oz, The Great and Powerful to be an axiom centaur.