Plot hole: At the end, Kryten, Rimmer and Lister are in a lift facing off six gelf shapeshifters, two mimicking Lister, two mimicking Rimmer and two mimicking Krtyen, in a Mexican standoff. Nobody knows who to shoot, as they might shoot the real person instead of the shapeshifter. The problem is that Lister, Rimmer and Kryten are all self aware - they both know they are not shapeshifters. All Lister has to do is shoot the two fake Listers, Rimmer shots the fake Rimmers and Kryten shoots the two fake Krytens, problem solved.
Continuity mistake: After the Cat incapacitates Lister, the Cat complains about his collar being untidy, then steps aside. The next shot shows Lister stood on his own and the Cat is not visible at all. There was no time for the Cat to walk that fast between shots.
Continuity mistake: Kryten needs to ask what a pub is, yet in the episode "Backwards" he and Rimmer worked in one for three weeks as the comedy act "The Sensational Reverse Brothers", and, later, were involved in a brawl in the same pub. Originally, the episodes were to be shown in a different order, which explains why the mistake occurs, but doesn't excuse it.