Many motions about aliens and robots are really debates about meta-ethics in disguise. Without using any jargon or requiring formal training in philosophy, they make us consider genuinely novel entities, and ask ourselves what moral obligations we might owe to them (or they to us). They are ideal debates to test moral reasoning from first principles, and the ostensible absurdity of their premises makes many of the cliché arguments seem out of place. No one will argue that we owe obligations to aliens under some mythical social contract.
I'd like to set debates about Chapter 3 of Kant's Grundlegung zur Metaphysik der Sitten, but that would be a bit unfair. So until such a time as we can run the Philosophy IV, I'll have to content myself with aliens and robots.