After an encounter with a deranged medical droid leaves him sans kidneys, Lister's only hope to survive is to somehow persuade the only other living biological creature on Red Dwarf to donate one to him. But that creature? Is the Cat.
This episode includes examples of:
- Acquired Situational Narcissism: When he realizes he really does have all the knowledge needed to be a successful engineer, Snacky grows rather contemptuous of fulfilling his original function as a snack dispenser.
- Ambiguously Evil: In light of the twist ending, it appears that Asclepius at the very least did not actually do anything to Lister and the Cat, and may even have been trying to help Lister.
- Bizarre Alien Biology: Invoked; the fact that Cat isn't human is explicitly called out as hugely problematic to the plan to transplant one of his kidneys, as they'd be genetically incompatible with Lister. Their hope is that "Asclepius" would be able to perform a special gene-modifying technique that'd fix the problem.
- Bookends: The episode starts and ends with Rimmer's interacting with Shaft 14, one of Red Dwarf's elevators.
- Call-Back: The stasis-pod-based temporal loops are akin to the "Stasis Leaks", from way back in Stasis Leak.
- The Ending Changes Everything: It turns out Lister already had no kidneys before Asclepius knocked him out, the implication being that if Rimmer and Kryten hadn't presumed that the kidneys they destroyed were Lister's the whole story would never have happened, and that Asclepius was actually trying to give Lister a life-saving operation.
- Laser-Guided Karma: Rimmer promises Shaft 14 that he'll not only rescind the demotion of his past-self, but also put him into the swanky shaft to the officer's lounge. Instead, he does no such thing. So, when he ends up inside of Shaft 14 again, guess who's just volunteered to test out Shaft 14's new nuclear reactor-powered counterbalance...?
- Mistaken Identity: Hilarity Ensues when Kryten and Rimmer mistake Snacky, a snack dispensing droid, for Asclepius, a super-advanced 23rd century medical droid.
- Never Trust a Trailer: The publicity for this episode played up Asclepius as being a far bigger part of the story than he actually was, and suggested that the main story would be Lister trying to persuade the Cat to give him one of his kidneys.
- Stable Time Loop:
- Romero Gonzalez came back to the past to warn himself that his stasis loop project would lead to him murdering himself. His past self promptly stabbed him to death.
- Exploited by the Dwarfers; rather than do the "transfer a gene-treated kidney from Cat to Lister", which is impossible, they instead go back in time to just before the whole mess happened, mug the past Lister, steal his kidneys, and graft them into future Lister.
- Unnecessarily Creepy Robot: Asclepius, the super-advanced medical droid, has a single massive eye that is Sickly Green Glowing, a mouth-grill that looks like an impossibly massive set of fangs curled into a permanent Slasher Smile, a body designed like a stereotypical Mad Scientist labcoat, one hand that's a rotating array of blades and pincers, and another hand that's basically a cannon. There is no reason for a healing bot to look anywhere near this creepy!
- You Are Better Than You Think You Are: Rimmer, of all people, manages to pull off a motivational speech to prove to Snacky that he assimilated a lot more engineering knowledge and skill from Gonzalez than he is willing to admit to himself.