Revealing mistake: When Holly gives Rimmer a new uniform, during the switch, Holly can be seen to jolt on his screen in the background. (00:03:20)
Revealing mistake: When Holly gives Rimmer a new haircut, Rimmer salutes and touches his hair with his hand. Surely he would have noticed his hair has become much longer, especially after he asked for a crew cut. (00:07:00)
Revealing mistake: In the drive room when Lister kicks the vending machine after he finds out he's going to die, you can see the shadow of the machine wobbling as if it were lightweight. (00:20:20)
Revealing mistake: When Rimmer runs to Lister after Lister unsuccessfully orders a black coffee, the camera tilts.
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.
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 ★