Other mistake: At the start of the episode, there is a spoof Star Wars-type caption, which spools up the screen very quickly. Too quickly to be read, in fact... which may explain why few people have noticed that the last line of the caption, "And now the Saga Continuums...", is written twice. (00:00:20)
Other mistake: When Rimmer is testing Kryten on a book of space traffic signs, Kryten stops on one page and is tested, which he says the sign is a binary star. Without turning the page, Rimmer points to a second sign on the same page asking what it is, which he points out is a blue giant about to supernova. After pointing to the time hole, Rimmer turns back to the book, saying "Right. What's this?" whilst still on the same page, pointing to a another sign. The page that is being used has one sign shown on the right hand side page, and the left hand side page is completely blank, equalling one sign on both sides of the page, but two or three signs are made mention to when on the page. (00:05:20)
Other mistake: It is established in the backwards version of Earth, that all writing is reversed and is spelled backwards. However, there are some inconsistencies, as in some instances the writing has been mirrored to appear reversed, whilst in some instances the writing has just been spelled out backwards. For example, car number plates and signs on display in the background have been mirrored to appear reversed, but the newspaper that Kryten reads, the Nodnol sign and the Sensational Reverse Brothers poster appear normally typed out, and not as the mirror image that other aspects of this world have.
Answer: The cello is a large four-stringed instrument, which, when it is played, stands vertically on the floor between the player's legs (assuming they are seated). If it is to grow as large as the other instuments mentioned will, it would require a rather unseemly lack of femininity to be able to encompass it with the legs.
Rooster of Doom