Continuity mistake: In the hologram simulation suite, the amount of smoke changes from cut to cut throughout the scene. (00:06:30)
Audio problem: During the conversation in which Holly wants to prove he has an IQ of 6000 (while Lister and the Cat are scrubbing the floor), there is a brief moment where you can see the TV Holly is on (at an angle). You can hear sound coming from him, but his lips aren't moving. (00:16:55)
Revealing mistake: When Holly shows the crew the Holly Hop Drive, you can see the outline of his black clothes throughout the scene. (00:06:35)
Revealing mistake: When Lister and Rimmer first meet their femaile opposites, Lister takes a step back and brushes against Rimmer's hologramatic shirt. (00:10:30)
Continuity mistake: At the disco, when the Rimmers are seated at their table, the plant moves from in front of the lamp to behind it. (00:15:40)
Continuity mistake: In the disco when Lister complains about the female Lister's attempts to impress him, his hair is in front of his left shoulder, then behind it. (00:19:10)
Continuity mistake: When the Cat jumps up to grab the mirrorball, a comb appears in his hand from nowhere before disappearing again. (00:20:25)
Continuity mistake: When the Cat dances at the disco, he jumps up and grabs the mirror ball with both hands. In the next shot he is only holding it by one arm. (00:20:25)
Continuity mistake: When Lister and Rimmer talk to Holly at the disco, Lister's arm is on the table. When the camera angle changes, it is on his lap below the table. (00:21:15)
Continuity mistake: In the quarters of the female versions of the crew, the newspaper clippings and certificates on the wall still have the name 'Arnold' on them, and not the female equivalent, as it was supposed to be. (00:23:15)
Visible crew/equipment: A wire/string pulling along the baby Skutters behind the parent Skutter is visible in the episode. (00:25:35)
Revealing mistake: During the last scene of the episode, the Cat keeps brushing against Rimmer's hologramatic shirt. (00:27:10)
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 ★