Lister's cast is missing for some shots when he is in the spacesuit. (Craig Charles was called away for the birth of his son, so production manager Mike Agnew stepped in and forgot to put on Lister's plaster cast.)
When Lister and Cat drop the gravestone, they both grab their left legs, but Cat has the cast on his right leg later.
When Rimmer is drunk and has just told Lister that he only made love once in his life, Lister steps up from his chair in a clockwise motion (Right leg first). Later, when they are watching the black box CCTV footage of the same incident, Lister is seen getting up and turning in an anti-clockwise motion (Left leg first)
Rimmer confesses he's only made love once. To Yvonne Macgruder. But in Marooned (1989) he says he lost his virginity in Cadet school to a girl named Sandra.
When Rimmer is lying on his bunk with his uniform all dishevelled, a Harrods label is visible on the back of his tie. Rimmer wears a Space Corps issued uniform, generated by a computer no less, so his tie probably isn't supposed to be from the famous London luxury department store.
Holly mentions Jimmy Osmond and Rimmer replies "Who"? In 'Polymorph', Rimmer describes the Polymorph as having "more teeth than the entire Osmond family".
Cat mocks Rimmer for his very low count of intimacy with women. He's one to talk, as with the likely exception of his own Mother, he has yet to encounter a woman. Let alone copulate with one.