Fan Casting Pinocchio Syndrome in Sort by Tropes

Whatever the reason, the nonhuman beings want to become human, or in the case of formerly-human beings, they want to be human again. Despite Applied Phlebotinum and magic being able to do everything else, it seems the power to turn someone into a mortal human being is incredibly rare. In those cases where those who do get the instant magical cure, they'll often throw it away, saying they want to earn it, or "it's the path, not the destination" (whatever that means), or it will come at a horrendous moral cost. In other words, Failure Is the Only Option, at least until the Grand Finale.