Kryten is tinkering with a new machine he has salvaged from the station, and as Rimmer enters, Kryten begins to explain to Rimmer what the machine does. It is a "Personality Tuck Machine", which scans the patient's psyche, forming a "mind map", and is then able to enhance, remove, or even sculpt the very traits that make that person who they are. Interested, Rimmer asks if Kryten thinks he could do with a bit of work, and Kryten says that he will cancel the rest of the weeks schedule as Rimmer takes a seat. As Kryten looks at the map of Rimmer's mind, he sees that it is made up of pomposity, self-importance and cowardice. Cat enters and suggests that personality surgery on Rimmer is a great idea. Rimmer is excited to become a brave and dashing version of himself, although he wimps out and runs away when Kryten produces a laser scalpel and a big syringe and says that it may sting a little. Kryten and Cat then discuss how Rimmer has broken the speed of light.
Soon after, in the cockpit of Starbug, Lister is fast asleep and snoring despite the fact the red alert bulbs are flashing and the warning klaxons are ringing. The other members of the crew bundle in, waking him up, although Lister asks them to stop making so much noise. According to Rimmer, Lister dozing off means the crew are now 5,000 clicks off course, and drifting dangerously close to some rogue asteroids. Rimmer blames Lister for their ship being adrift, whilst Lister blames Kryten for the astounding amount of food Kryten cooked him earlier, which along with the beer that Kryten gave him made it impossible for Lister to stay awake. Lister says that it was the biggest Sunday lunch he has ever had, and asks Kryten how long he has been out - while Kryten informs him that it is Monday.
As Rimmer bemoans how long it will take to get back to Red Dwarf, Lister suggests taking a shortcut through an asteroid belt Kryten identifies as Juno 98. Rimmer realises it is GELF country. Kryten starts to tell of ancient astro myths about the asteroid belt, but then sits on a screwdriver. He finally explains that the particular tribe who inhabit Juno 98 are the Nakhi Ninkas, more commonly known as "vampire GELFs" and which only feast on the blood of virgins. As both Lister and Rimmer have had sex, and Kryten is a mechanoid, they are all safe. However, the Cat is a virgin, despite the way he tries to disguise it by pretending he has two female Felis sapiens lovers back in Red Dwarf on Z Deck. Lister says he will take Starbug into Juno 98, but the Cat makes vehement protests. Kryten tells the crew that the Nakhi Ninkas smell the virgins from the non virgins, as the virgins "smell" of fear, due to a pheromone that virgins produce. Rimmer begins to mock the Cat, saying that his only love affair has been with a mirror, and Lister tells Cat that he will take Starbug the long way round the asteroid belt.
Suddenly, the navicomp of Starbug detects up a nearby spacecraft with an energy signature that is barely registering. Although Rimmer is scared that it could be a GELF battle cruiser and orders him not to, Kryten has already hacked its mainframe and learns that it is not a GELF ship, but actually a transport ship with a crew of two - one Mercenoid guard, and one prisoner of indeterminate nature. Kryten and Lister are familiar with Mercenoids, believing them to be fairly deranged. Realising that the transport is on a death dive into a super-massive Black Hole, they decide that they will board the transport ship to rescue whoever the prisoner may be, since Lister believes it may be human.
As usual, Rimmer is scared and stays aboard Starbug to guide the others remotely as Lister, Kryten and Cat board the transport ship armed with bazookoids. Rimmer continues the hack of the transport mainframe, telling the others of the new intel as they search the ship. Apparently, it was transporting scientific equipment to a bio-station on Orta 15. However, nothing else is available, since the log and Black Box have been erased. As the others enter corridor Beta 12, Rimmer panics, telling the others that something organic and part organic is right in their location - sending the others into a panic too - before realising that Rimmer is actually seeing Lister, Kryten and Cat on the radar.
Going deeper into the transport ship, Kryten picks up EM emissions on his Psi-Scan, and they move towards it and eventually they bump into the Mercenoid, who is armed with an energy weapon. Hiding round the corner, Lister tries to ask it who its prisoner is and what crime they have committed, but the Mercenoid merely says that is its own business. Lister proposes a trade, but the Mercanoid refuses, and orders the "humies" to take its advice, and leave or die. Lister rounds the corner with his bazookoid, telling the Mercanoid to drop its weapon, but instead it opens fire, narrowly missing Lister and hitting a pipe instead. However the Mercenoid is distracted by a human voice - which turns out to be Rimmer's dictaphone that Lister had thrown a short time earlier, and contains recordings of Rimmer talking to himself about how he is beautiful, and how size doesn't matter. The Mercenoid is tricked into picking up the device, which backfires with a massive electrical burst, activated by Lister remotely, and completely disables the Mercenoid.
They move up two floors to Bay 12, where the holding cells are, and find the prisoner. Much to the Cat's amazement and excitement, the prisoner is a female Felis sapiens named Ankita, identical to Cat in personality and dress sense. Cat blasts the emitter which generates the laser bars of the cell, freeing her, and the group then quickly head back to Starbug, leaving the transport to fall into the Black Hole. They then begin the journey of heading back to Red Dwarf; all the while, Ankita behaves the same as Cat, "claiming" everything as her own. Back onboard Red Dwarf, as Kryten prepares some quarters for Ankita, Cat and Ankita arrange to have a date, involving the string game, at eight o'clock.
Kryten, however, finds something deeply disturbing as he recovers data from the Mercenoid's Black Box in the Science Room, and calls down Lister and Rimmer claiming an emergency. Ankita was not actually a Felis sapiens, but in fact a female polymorph, carrying eggs - morphlings. Rimmer realises that is the reason why the Mercenoid was in a kamikaze-style death dive into a Black Hole - since the Mercenoid was trying to completely destroy the polymorph too. When Lister asks what Ankita's motives could be, Kryten explains that female polymorphs look for a host body to deposit their eggs in, before expiring. To demonstrate this, Kryten brings up an "genetic mutant documentary" on the RedNet and displays it on the monitor. The documentary is narrated David Attenborough-style, and the gang watch a very gruesome scene of polymorph births.
Suddenly realising it has gone eight o'clock, they panic and locate Cat in Lister and Rimmer's bunkroom. They are evidently too late, since the Cat is in a very happy and giddy mood, eating, twirling around and singing Oh, What a Night. Cat says that the sex was amazing, even when after blowing on her "antennas" Anikta's "giant pipe thing" shot out of her back and down his throat, releasing "gushy tadpole stuff". When she said that she had never met anybody who could hold so many eggs, Cat didn't know what it meant, but assumed it meant he had "done good". The others explain to the Cat that Ankita was in fact a polymorph, and repeatedly call him a moron, to which he replies with the fact that it still counts as having sex. They go off to Ankita's quarters to kill the polymorph, but she is already dead (and reverted to her real, disgusting form), her life cycle complete.
After doing an ultrasound in the Science Room, they discover that the Cat is pregnant with a staggering EIGHT polymorph morphlings, each of which will explode out of his body when ready to hatch, without even forming an orderly queue. The crew deliberate on what to do, as the Cat starts to have convulsions. Rimmer runs away, as per usual, claiming he is glad that he didn't have his cowardice removed earlier. Lister and Kryten decide the best thing to is let the Cat have a Caesarian section - which Cat agrees to, but without croutons. Kryten prepares the laser scalpel, which he cannot control, almost destroying the Science Room and killing everybody along with it. Unfortunately for them, the morphlings have changed into tumors. If Kryten kills them with a laser, they kill the Cat. The crew come to the conclusion that the best thing is to let the morphlings be born in the "normal" way, but make sure they all come out of one hole - Cat's rear. Lister claims it will be no different to when he has a curry.
Within a few weeks, the Cat becomes very large, heavy and quite clearly pregnant. He then enters labour as he watches television with Lister in the bunkroom, who rushes Cat down to the Science Room to have a water birth. The eight morphlings immediately change shape, exiting the Cat in ever-more painful forms such as a set of gnashing teeth, a pineapple, a toy boat, and a space hopper. As Rimmer paces outside, Lister and Kryten place the morphlings into a box, and they all continue to change shape.
Cat survives the births, and the crew decide to flush the morphlings out into space. As they reach the airlock, the morphlings adopt the forms of adorable and cute animals as part of a defense mechanism. This includes a baby piglet with a blue bow, a hamster on a skateboard, a chinchilla with a pink hat, two Dalmatian puppies, a fluffy white kitten and a top-hat wearing hedgehog sat in a miniature shopping trolley. Even Rimmer turns gooey for a moment. Kryten reminds them that they will become shape-shifting, evil monsters, and that even the Rolling Stones were cute when first born. The Cat explains to the crew that he will flush them out himself, and wanting a minute alone to say goodbye, asks the others to leave the corridor. The crew find that he is taking a long time, and look to see that Cat has already left through the elevator with the morphlings.
Kryten theorises that Cat has succumbed to the powerful hormone oxytocin secreted by the morphlings, which ensures that the host looks after them and will not let them come to harm. Rimmer comes up with a plan - turn off all the heat inside Red Dwarf, except in the Diesel Decks, so it will drive them down there and narrow down the search. Kryten suggests that, since polymorphs can sense the emotions of others - and feed off them - they use the Personality Tuck Machine to alter Lister's personality, removing any emotion and making him undetectable to the polymorphs.
The enact this plan, and then head down to the Diesel Decks, where two different versions of the Cat jump out. Without stopping to check, Lister immediately kills them both with a handheld bazookoid, exploding them in a shower of green goo, with Lister explaining that he doesn't care if they were even really Cat or not. Kryten and Rimmer realise they have altered Lister into a sort of polymorph, no emotion, but without the shape shifting effect. Kryten supposes that Lister may actually be one of the polymorphs, since they are notorious for killing their siblings to remove competition.
The crew turn on each other, wondering if they are polymorphs or not. Two more versions of themselves appear, and do the same, resulting in a Mexican standoff between all nine of them. Kryten argues that they should go back up to the Science Room and x-ray each other to find out who is a polymorph and who is not. They all move into the elevator, all still shakily pointing their guns at each other.
The doors then open, revealing the real Cat, looking forlorn at the floor. Then, in a heartbeat, Cat looks ups and shoots the other six polymorphs in the lift, including doing some acrobatic shooting. The real Lister, Rimmer and Kryten, all covered in green goo, are amazed and ask Cat how he knew who everybody was. Cat explains that a "mama always knows her kids".
The episode ends with Lister entering the Cat's quarters to have a conversation about him being a virgin. Cat is in bed, and moans that he is trying to sleep. Lister says that it is OK to be "that thing that you're not", that it doesn't make him a loser, and that he just hasn't met the right girl yet. The Cat says he isn't, and then tells Lister to leave. As he leaves, two female Felis sapiens in a state of semi-dress emerge from the Cat's bed, and bemoan Lister's annoying, condescending habits. The Cat asks if this is a dream, and the two woman nod and smile. He then asks them to "pipe" him.
- Craig Charles as Dave Lister
- Chris Barrie as Arnold Rimmer
- Danny John-Jules as The Cat
- Robert Llewellyn as Kryten
- Bently Kalu as Mercenoid
- Dominique Moore as Ankita
- Daniel Barker as Alien Natural History Presenter
- Maria Yarjah as Cat Lady 1
- Shanice Stewart-Jones as Cat Lady 2
- An alternate and slightly lengthier shoot of the opening scene to the episode aboard Starbug. One of the most notable differences is that the "Meta-Station" is alternatively referred to as the "Medi-Station". There is also slightly more explanation as to how the Personality Tuck Machine works.
- As the Cat panics at the thought of the "Vampire GELFs" due to the fact that he is a virgin, and Lister says that he will take Starbug the long way around their asteroid belt, Rimmer jokingly says that they are taking the "Virgin Highway". "Avoid Route 69". Getting annoyed, Cat again angrily denies that he is a virgin, and shows Rimmer an engagement ring on his hand, asking Rimmer where he thinks he could of got it from. Rimmer asks if Cat proposed to his hand, or if his hand proposed to him. Even Kryten begins laughing, although Lister starts to get over protective of Cat and asks the others to back off.
- In the Science Room aboard Red Dwarf, as they are examining the pregnant Cat, Kryten says that he is going to place a probe on Cat's stomach. Cat complains at how cold it is, and says that it better not leave a mark since it could ruin his whole body. Rimmer says that Cat hasn't seen nothing yet.
- The title of the episode comes from a line said by Lister, when he says that he is "sorry to open a can of worms" when discussing Cat's supposed virginity. "Opening a can of worms" is a metaphorical phrase of speech or idiom similar to "opening Pandora's Box", or "the Genie is out of the bottle".
- Despite being billed as the long awaited Cat episode, the episode instead switches to being a third Polymorph story, following on from the original "Polymorph" in Series III and "Emohawk: Polymorph II" from Series VI. The last time the creature was mentioned was as a casual aside in Back to Earth. The visual effect used for the morphlings changing shape is closer to how they were presented in the original Polymorph episode than the CGI effect used in Emohawk.
- The idea of the Cat meeting and seducing a lady Cat is reminiscent of the lost episode of Series VII titled "Identity Within", while the Cat's pregnancy is somewhat similar to material touched in the lost Series III episode "Dad" as well as the cliffhanger ending of Series II "Parallel Universe".
- The fact that the Starbug in this episode is numbered as Starbug 19 would suggest that somehow they had recovered the fleet of shuttles which fled Red Dwarf with the nanobot-resurrected crew in "Only the Good..."
- In a rare moment of self-parody, Kryten sits on a screwdriver while trying to pronounce the GELF race name Neki-Nenkas. This causes him to go into a cacophony of "ech-ech" noises, much like those uttered by the crew when dealing with GELFs in Series VII.
- Kryten is as undisturbed by the vampire GELFs as Lister, who lost his virginity to Michelle Fisher aged 12 (RD: Marooned), and Rimmer, who lost his to Yvonne McGruder (RD: Thanks for the Memory), are. Either Kryten is himself a not a virgin, despite his much remarked upon lack of sexual organs, or he simply assumes mechanoids do not count. His only depicted romantic relationship was with Camille, a Pleasure GELF, who likewise described her/itself as adroginous (RD: Camille).
- Although it only happens in a dream, this episode marks the first appearance of the Cat's quarters, as well as confirmation of the fact he actually has quarters (previous episodes having implied he simply slept where he wanted).
- Sequences on the transport ship borrow heavily from Aliens, both thematically and visually, and the Polymorph being held in Bay 12 is almost certainly a reference to Sgt. Apone's line in the film, "Bay 12, please!"
- Lister: "Woah, what's going on here, who's the joker in charge of navigation?"
Kryten: "You are, sir!"
- Cat: "Smell 'em! What the hell does a virgin smell of?"
Lister: "Desperation, normally."
- Cat: "I've had my share, let me tell you! More than my share! Plus I've had full blown love affairs too!"
Rimmer: "Well, yes. Mirror in the bathroom, mirror in the hall. I'd forgotten about those."
to be completed