Plot hole: At The End, Kryten, Rimmer and Lister are in a lift facing off six gelf shapeshifters - two copies of each real person, in a Mexican standoff. Nobody knows who to shoot, as they might shoot the real person instead of the shapeshifter. But the real people know they're real - all Lister has to do is shoot the two fake Listers, Rimmer shoots the fake Rimmers and Kryten shoots the two fake Krytens, problem solved. Not to mention Lister is now a soulless, unfeeling killing machine. Earlier he shot and killed a shapeshifter who could well have been Cat - he didn't know it was a shapeshifter and by his own admission he didn't care. We have already seen how fast on the draw he is - why didn't he just open fire on the six shapeshifters, Kryten and Rimmer in order to ensure his own survival?
Suggested correction: The point of a Mexican standoff is no one is in a position to shoot first for fear of being shot themselves. We're told the shapeshifters have no problem killing each other, so as soon as the real person starts to shoot, everyone may start firing, which could result in a real person being killed. Additionally, the only time all 9 are pointing guns at each other is in the lift. Before that, it's 3 groups of Listers, Krytens, and Rimmers, so no one is facing off with their shapeshifters. The only safe way to shoot the 6 shapeshifters would be to do it at the same time, and there's no way Lister, Kryten, and Rimmer could coordinate that. And, like all Mexican standoffs, it can only be resolved from outside help.
Factual error: Kryten tells everyone that the matter paddle transmits matter in digital form from one place to another at the speed of light - he is very clear on this point. He then locates Waxworld, which is 200,000 light years away. Okay - so when they use the matter paddle to transmit themselves to Waxworld, why doesn't it take them 200,000 years to get there?
Suggested correction: Kryten says that the paddle sends them via subspace, so they will reach it almost instantaneously (rewatch the scene, he never says they'll travel at lightspeed).
Plot hole: Right after the shrinking boxers scene, Kryten says the small boxers are missing from the bunk, but you can see them right in front of him. (00:10:00)
Suggested correction: I've just watched this scene. You're mistaken. The boxers aren't visible when Kryten turns back to the bunk. The trunks were bright red. The only red thing visible in the scene where Kryten is looking at the bed is the "no smoking" sign, which is on the side of the bed, right in front of him.
Plot hole: In the last series, a point was made that the time drive is not a teleporter, so can only send them backward and forward in time in the one location (Deep Space). So in this episode, how can they now travel to Earth with the same device?
Suggested correction: With the merging of the two universes, the time drive ended up with the faster-than-light drive from the other universe (which is also how Starbug ended up bigger).
Other mistake: In the picture of the cat wars between the Red Hats and the Blue Hats, the hats are orange instead of blue. (00:19:00)
Suggested correction: Cats are colour blind.
Trivia: On the DVD, you can watch this episode backwards. This way, not only can you find out roughly how they made this episode and find out what 'reversed' people are saying, you can hear someone shout 'ACTION' right before the brawl scene.
Suggested correction: This episode is available backwards on YouTube, too.
Revealing mistake: At the start in the cockpit of Starbug, the green screen behind Lister is visible instead of the painted starfield that should be there. (00:02:35)
Suggested correction: That is because Starbug is parked inside Red Dwarf at the time, and the stars wouldn't be visible.
Continuity mistake: Just after The Inquisitor is frozen when Lister and Kryten switch gauntlets, the glove gets onto Kryten's hand in one camera cut. (00:24:30)
Suggested correction: He's holding the gauntlet in his hand, but the angle of the camera makes it appear that he's wearing it.
Continuity mistake: In the forest, Lister and the Cat take a poster off a tree. They then show it to the man who gives them a lift. The poster is different to the one in the forest. (00:16:05)
Suggested correction: If you look at 00:13:47, you'll see that the closest tree has an odd poster. The other trees have the poster that they showed to the man that gives them a lift.
Plot hole: The man the crew find stampeded to death had been lying in the road for a year, yet he had not began to decompose. (00:17:50)
Suggested correction: There's nothing stating that the body had been lying in the road for a year. Rimmer says it looks like the man was trampled to death in some kind of stampede, but it isn't confirmed if that's how he died (Rimmer is often wrong about many things), or when it might have happened.
Emohawk - Polymorph II - S6-E4
Revealing mistake: Both Ace and the Emohawk get sprayed with the liquid Dyllinium, yet only the Emohawk becomes paralysed. (00:26:55)
Suggested correction: Ace is a hologram. Even though he is hard light, he cannot be harmed. Which is why he was able to jump on the grenade and not be harmed. So the gas spray wouldn't have harmed him either.
Plot hole: Pete the sparrow was dead before the time wand was used on him to become a dinosaur. When the undo button was pressed, Pete should have turned back into a dead sparrow. (00:23:10)
Suggested correction: Unless the "undo" time on the wand was set to shortly before he died, it isn't explained exactly how the wand works or what the control options are, so it's possible.
Plot hole: At the start of the episode, on a shelf in the sleeping quarters is one of Rimmer's Army De Nord figures, which were all burned in Marooned in series 3. (00:00:40)
Suggested correction: Obviously, he has more of the figures than those that were in the chest; it's never stated that he doesn't, and he missed at least that one when packing.
Other mistake: When Rimmer tries to silence the vending machine, he covers up the input microphone with stickers instead of covering the speaker just above it. (00:05:05)
Suggested correction: This isn't a mistake. There's no evidence that the speaker is just above the microphone (the "speak here" grill). The vending machine tells Rimmer to take his hand off its speaker when his hand is over the "speak here" grill. This suggests that the grill covers both the microphone and speaker.
Continuity mistake: When the Cat picks up the golf clubs, his hair is sitting on his left shoulder. In the next shot it is behind his back. (00:10:40)
Suggested correction: His hair moved to his left shoulder when he turned his head and picked up the clubs, but you can see his hair go back behind him when he straightens his head.
Factual error: The polymorph goes through a metal pipe and a tap which bulges and becomes mis-shapen. The tap then changes back to its original shape, which is impossible. (00:18:00)
Suggested correction: It's impossible using today's technology, but maybe not in the future. Maybe they have metallic-like materials that flex back to a previous form after deformation.
Revealing mistake: When Baxter puts the Cat's head in the drinks machine and says hot bovrill, Kryten can be seen mouthing the line behind him. (00:22:20)
Suggested correction: Kryten is not mouthing the line "Hot bovril." He is just moving his mouth slightly up and down, which coincidentally happened to occur when Baxter was saying the line.
The Last Day - S3-E6
Plot hole: In this episode Kryten has no idea how to operate a bazookoid, yet earlier on in 'Polymorph' he was able to change the settings of one from standard to heat-seek and fire it without a problem. (00:24:45)
Suggested correction: He's in a panic. People, even mechanoids apparently, forget things in a panic.
Plot hole: Lister is not allowed any dangerous objects that he might try to commit suicide with, yet when he is with the canaries on their missions, he carries an assault rifle. The canaries aren't always supervised and it would be impossible for a guard to stop any of them putting a gun to their head and pulling the trigger. (00:05:05)
Suggested correction: We only hear from Rimmer that that's a rule. Rimmer is usually wrong about most things.
Suggested correction: Lister can only see M-Corp products and M-Corp employees. Cat is not an employee of JMC or M-Corp, so he disappears. Lister is the only member of the crew who is employed by M-Corp at this point.
Suggested correction: Cat was a descendant of the cat Lister brought aboard Red Dwarf. Would it be possible that the new owners might have stricter security controls, and Lister was sent to Stasis for a different reason?
Andy Benham ★
Inventing Deux ex machina explanations for a plot hole doesn't make it any less of a plot hole. M-Corp erases all of the Jupiter Mining Corporation's equipment, personnel and infrastructure from Lister's life. In no way is Cat a part of that. He has no connection at all to the Jupiter Mining Corporation, and until he meets him in Episode 1 no connection to Lister, either.
If M-Corp only erased JMC equipment from Lister's life, then Kryten, who belongs to DivaDroid and not the JMC, wouldn't have disappeared either. He disappears as he doesn't belong to M-Corp, not because he belongs to the JMC. Cat has no connection to M-Corp, as he wasn't a part of the JMC (as you pointed out), and is therefore erased for Lister.