Revealing mistake: When Lister goes to Rimmer's room the second time, the door opens before Lister hits the switch.
Revealing mistake: When the future echo Rimmer leaves the drive room and the actual Rimmer walks in, there is a visible line caused by the split screen effect, done to show two Rimmers onscreen at the same time.
Confidence and Paranoia - S1-E5
Revealing mistake: When Confidence is trying to get Lister to take his helmet off, Lister climbs over a railing and jumps around him. It is clear that the footage of Lister jumping around was slowed down to make his movement appear as if there is a lack of gravity. (00:26:35)
Chosen answer: In-universe, after leaving Red Dwarf after his first appearance, Kryten managed to crash Lister's space-bike into an asteroid. Lister found his remains and decided to rebuild him, however, due to the high level of damage and Lister's questionable repair skills, he was unable to recreate Kryten exactly, leading to changes in appearance, personality and accent. In reality, the original actor wasn't available, coupled with presumably practical concerns about one-off makeup as opposed to makeup for a regular cast member, so some visual changes were made.
Tailkinker ★