An insane GELF escapes from a Genetic Waste Pod known as a Polymorph (created as the ultimate warrior, which can change its own shape to "suit its terrain and deceive its enemies") infiltrates Red Dwarf from the nearby containment pod by chewing a hole through the hull in one of the cargo decks.
Meanwhile, in the Officer's Quarters, Dave Lister (Craig Charles) cooks his "Shami Kebab Diablo" (which once put Olaf Petersen in sick bay for a week) for himself and the Cat (Danny John-Jules). After his attempt at more "classy" dining involving using items from the medical unit, including a bovine artificial insemination syringe to serve lemon juice, puts the Cat off, with him calling it more of an autopsy than a meal. Kryten (Robert Llewellyn) finishes off the cleaning of the Officer's Quarters with his Groinal Attachment.
When the Shammi Kebab Diablo jumps off the plate and around Lister's neck, Lister throws it across the room. Putting on his boxer shorts, they suddenly begin shrinking around his groin, and Lister falls to the ground as he attempts to remove them. As Lister pleads for Kryten to help take them off, Arnold Rimmer (Chris Barrie) walks in and gets the wrong impression, saying that he's not surprised since Lister will bonk anything. The boxers then turn into an anaconda, Lister's second worst fear, and then into an "8 foot tall armour-plated alien killing machine" (his worst fear) taking Lister to the very limit of terror. The polymorph then drains Lister of all his fear with a plunger-like tongue on Lister's forehead. It then quickly escapes from the quarters, leaving Lister unconscious.
After Kryten explains what the polymorph is and that it feeds on negative emotion, Lister wakes up wanting to fight the polymorph - saying they should get out there and "twat it" - and also fight everybody in the Science Room. Kryten sedates him, and Rimmer says their plan should be to "run away", and so they go down to the shuttle hangars. As they load up supplies from the cargo bay, the Cat is forced to run from their own accidentally-fired heat-seeking bazookoid fire, although with his lightening reflexes the Cat is able to trap the fire-bolts in an airlock.
Full of pride, Cat is seduced by a woman, Genny. Genny reveals herself to be the genetic mutant, but Cat doesn't click on, and after offering sex and inflating his ego, proceeds to drain Cat of all his vanity. This turns Cat into a very out-of-character drunken, smelly tramp with a low opinion of himself. Kryten and Rimmer then find him, and Rimmer tells Kryten it is his fault as he let the Cat run off alone, causing the mechanoid's guilt chip to go into overdrive. Rimmer reveals himself as the Polymorph and drains Kryten of all his guilt, breaking Kryten's programming. Kryten immediately develops a selfish and insulting demeanor, and no longer cares about his crew-mates, instead planning to offer them up to the Polymorph at bazookoid-point if it will let him go.
The go back up to the Science Room and meet up with Lister to find Mrs. Rimmer sleeping with him, which contradicts Arnold's "very prim, very proper, almost austere" view of her and enrages Rimmer. When she tells him how Lister made love to her using Alphabetti Spaghetti Rimmer blows his top and the polymorph (who was in Mrs. Rimmer's form) drains Rimmer of all his anger.
Later the crew meet up to discuss their next move and Holly tries to rally them to fight the Polymorph while it rests after its four-course meal, however being drained of their emotions means they don't get very far in preparing a plan of attack; Lister is determined to take out the Polymorph through the most violent means possible (especially if he gets the chance to kill himself in the process), Rimmer is now a glasses wearing pacifist who plans to hit the Polymorph with a leaflet campaign followed by benefit concerts, the Cat feels he is too worthless to venture an opinion and Kryten is too busy dishing out insults and working out if he can survive by sacrificing the others to offer any kind of valid opinion. It's eventually decided, in lieu of an actual plan, to head down to face the Polymorph and hope for the best.
They all go off to the cargo bays to hunt down the polymorph, but accidentally release from the airlock the (still-active) heat-seeking bazookoid shots which the Cat evaded earlier and trapped in the airlock. With a quick duck, the released bolts hit the polymorph which was emerging in full form behind them, exploding it.
The polymorph's demise instantly restores their altered personalities, and Kryten offers to commit suicide due to the guilt, and Cat and Rimmer are horrified as to what they are wearing. As they walk off, it is then revealed that a second polymorph has also arrived, and the second one turns into Lister, smiling.
The second polymorph is not seen again. In the remastered version, it is explained that the second died of old age in Lister's clean underpants drawer.
As available for viewing on the Series III DVD:
- Extended dialogue in the "lunchtime with medical equipment" scene, and also a story about Lister's friend Olaf Petersen who spent a week in sick bay after trying Lister's Shami Kebab Diablo.
- The full, uncut growth of the Polymorph to it's real size. The initial transition was much slower, and more "toothy" and slimy, in the original edit.
- A lost Holly moment is followed by a fuller version of the Cat's conversation with the Genny the mutant.
- A lost bit of dialogue expanding on Kryten's new guilt-free nature and Cat with no vanity, as Kryten insults him and Cat agrees.
- This episode revealed that Rimmer was tormented by his brothers and that his mother had no time for him (or more specifically she "despised idiots, no time for fools").
- This is the first appearance of Kryten's groinal attachment.
- The shot in which the polymorph grows to gigantic size and sucks Lister's fear out of him reveals an aspect of Lister and Rimmer's sleeping quarters (in this case the Officer's Quarters) which is otherwise never evident on screen: that it apparently not only has a very high ceiling, but also sky-lighting.
- In the early 1990s, Red Dwarf aired in Canada on YTV, a channel aimed at young viewers. While the network usually had to exercise some censorship in terms of language or other content, they evidently gave up trying to make "Polymorph" a family friendly episode, and so it never aired on YTV.
- Although logically one would assume the fearless Lister would say he planned to "swat it", referring to the monster, the DVD subtitles and chapter titles confirm he does, indeed, say "twat it". (In context "twat it" would seem to be the more appropriate response for Lister as opposed to "swat it")
- This episode continues the trend in Series III of the writers ignoring the fact that Rimmer, being a hologram, should not be able to touch, or be touched, by any solid matter (indeed, this is a major element of several upcoming episodes). Yet the polymorph is able to touch Rimmer's forehead with its probe and suck the anger out of him, even though, being light generated by Holly, none of this emotion should actually reside where the hologram is. In the novel Better Than Life, it is more realistically stated that it ventured up into the Holographic Projection Suite. In this case, it could have sucked the emotions out of Rimmer's light bee.
- In the novels, it was Talkie Toaster who killed the polymorph, by decapitating it with his bread tray.
- According to Craig Charles on the DVD commentary, at least one viewer was upset enough by the acronym of Rimmer's suggested anti-polymorph organization (which happened to be the same as that of a female sexual organ) that she refused to watch Red Dwarf hereafter, citing her horror at a question about it being raised by her young daughter.
- With the second polymorph, there's nothing to say that the same one sucked the emotions throughout the episode.
- Rimmer: Well I can't say I'm totally shocked... You'll bonk anything, won't you, Lister?
- Lister (without his fear): I say lets get out there and twat it!
- Rimmer (without his anger): David. David. Do you have anything to bring to this forum? (While discussing how to beat the Polymorph)
Lister (without his fear): Yes, I have actually, Arnold. Why don't we go down to the ammunition stores, get the nuclear war-heads and strap one to my head?! I'll nut the smegger to oblivion!
Rimmer (without his anger): Right, well, th-th-that's very nice, David. Let's put that on the back-burner, shall we?
- Rimmer (without his anger): ...Um, I think we're all beginning to lose sight of the real issue here, which is: what are we going to call ourselves? And I think it comes down to a choice between "The League Against Salivating Monsters" or, my own personal preference, which is "the Commitee for the Liberation and Integration of Terrifying Organisms and their Rehabilitation Into Society". Um, one draw-back with that, the abbreviation is "C.L.I.T.O.R.I.S.".
- Mrs Rimmer: ...The things this boy can do with Alphabetti Spaghetti.
Rimmer: Alphabetti Spaghetti!?
Director Ed Bye drew inspiration for the look and design of the episode from watching the 1979 film Alien just before shooting began. For the cargo bay scenes a warehouse in Manchester was hired for the shooting. Empty cardboard boxes were strategically stacked up and down the warehouse floor to give the illusion of a stocked cargo bay.
Although the episode had a pre-credits warning, about the episode's content, this was more of a plot device as the episode was broadcast past the 9:00 pm watershed. During the filming of the Polymorph morphing into Lister's boxer shorts scene the audience laughed so loud for so long that Chris Barrie had to wait several minutes until things had calmed down (the scene is now considered by many to be one of the funniest of the entire series). This also provided extra work in the editing room as the sequence required more work than usual to edit together a workable shot.
The episode also had some of the show's most effects intensive scenes done yet. Animatronic versions of both the small and large Polymorph creature versions were created. The small version was voiced by production manager Mike Agnew. The larger model, which was prone to tipping over, collapsed before the final shot. Blue screen was used to shoot the creature and added to existing footage of the crew. To achieve the Polymorph morphing into all the different objects the traditional locked-off camera and jump-cut procedure was used.
The newly introduced Bazookoids provided more video effects as two heat-seeking laser bolts were fired and ended up chasing the Cat. The heat-seekers were given sound effects borrowed from the lightsabers of Star Wars (but given unique sounds in the Red Dwarf Remastered version of the episode).
- Frances Barber as Genny the Female Genetic Mutant who takes the Cat's vanity
- Simon Gaffney as Young Rimmer
- Kalli Greenwood as Mrs. Rimmer
- The theme of the episode is a parody of Ridley Scott's 1979 Alien film which features a Xenomorph. The Polymorph's transformations also resemble the Alien's various transformations, from the early small worm to its large incarnation with a huge jaw holding an extendable emotion sucking tongue.
- Rimmer also says "What about the Rimmer directive, which states never tangle with anything that's got more teeth than the entire Osmond Family." This a reference to the band.
While they were discussing how to handle the Polymorph, Lister shouted that "It's Clobberin' time," the catchphrase of the Thing of Marvel Comics' "Fantastic Four".
Rimmer suggests running away and the crew agree, yet in the next scene they are going into the Cargo Deck in pursuit of the polymorph (although this is explained in the Red Dwarf novel Better Than Life when they go to the Cargo Deck to gather supplies to wait the Polymorph out, it is possible that in the episode "Polymorph" they were in the Cargo Deck for similar reasons).