Revealing mistake: Crawford goes through the teleport to transport herself to the Space Station. But in the next shot, Crawford can be seen quickly leaving the shot as if she's still there. (00:23:05)
Revealing mistake: When Pree shows Lister his Medi-Bay file, it is a flipped shot. Note the danger sign next to the computer. (00:27:40)
Revealing mistake: When they change Professor Edgington from ape form to human form, the human form is obviously a lifeless mannequin. (00:23:35)
Other mistake: When Cat picks up the can of Leopard lager which is invisible to Lister, he shakes it, pops the cap and sprays Lister with foam. The foam is visible but the can remains invisible, and that makes no sense. If we are seeing the scene from Cat's point of view the can and foam should both be visible, and if it is from Lister's then neither should be.
Quarantine - S5-E4
Kryten: What a smee... What a smee... What a smee - hee.
Trivia: It was rumored that Alfred Molina and Alan Rickman wanted the part of Rimmer. Lee Cornes also auditioned for this role (he later guest starred on the show), as did Hugh Laurie. Robert Bathurst, Norman Lovett and David Baddiel auditioned for the role of Lister.
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 ★