Revealing mistake: When Rimmer stands up from underneath the table, just before he says, "Thanks for your support" to Lister, listen very carefully and you can hear the stunt director saying "Action!" backwards. This shot was the splice point between the reversed and the regular footage. (I know this mistake is listed as being in the 'backwards version' on the DVD, but it is in the regular broadcast version too - you just have to listen harder for it.)
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.
Revealing mistake: When the Polymorph, posing at the snake, jumps on Lister, it is apparent that the snake on Lister has been replaced by a plastic inflatable replica that has no features and does not move. (00:10:05)
Revealing mistake: When Rimmer is piloting Starbug in Lister's body, there is a shot of Starbug spinning in circles. This is a shot that was taken from S3 E2 Marooned, of Starbug crashing after colliding with the asteroid. The only difference is the planet in the background has been changed. (00:22:10)
Revealing mistake: During the chase on the moon, there is a shot from in front of Starbug crashing into an asteroid. About twenty seconds after this, the exact same shot of Starbug crashing into an asteroid is been repeated a second time, when the ship crashes. (00:23:20)
Revealing mistake: Starbug and Blue Midget wobble on a number of occasions during the chase. (00:23:25)
Timeslides - S3-E5
Revealing mistake: When Lister is hit in the face with the snowball, some of the snow lands on Rimmer's hologramatic uniform. (00:07:40)
Timeslides - S3-E5
Revealing mistake: When Rimmer dies at The End of the episode, a dummy is visible just before the explosion. (00:26:40)
The Last Day - S3-E6
Revealing mistake: You can tell Robert Llewellyn is reading his lines when Kryten receives the computer chip. He is looking much lower than the chip in his hand and it was obviously quite a complicated piece of dialogue to remember. (00:12:35)
Revealing mistake: The metal shelf the three spare heads sit on can be seen to move as spare head three speaks. (00:19:40)
Revealing mistake: When it is revealed that the DNA modifier has made Lister smaller, Rimmer, Cat and Kryten all have shadows cast on the floor, but Lister does not. (00:25:25)
Revealing mistake: One of the escort boots passes through a wall as it goes round a corner. (00:10:10)
Revealing mistake: When the simulant pulls the knife out of his chest, you can see the knife is a dummy. As the handle is pulled back, the blade does not move at all. (00:25:30)