Revealing mistake: During the 'Two Listers' scene, specifically the cut when Kryten tosses the apples to the Listers, the split screen is quite visibly moving in between the chairs. (00:22:55)
Revealing mistake: When Legion places the hard light in Rimmer's light bee, it is noticeable that the hard light does not go inside the device. It is placed more to the area beside it. (00:09:55)
Continuity mistake: When Rimmer suggests bringing Legion with him, Lister says he's not going to come with them, and asks if he would ever join in on their late night sessions of pin the pointy stick on the weather girl. At The End of the line, Lister is looking to the right, but in the next shot, he is suddenly looking downwards. (00:12:35)
Continuity mistake: When Legion brings the feast, Kryten is stood by the door. Rimmer says about how he appreciates art, then in the next shot of the Cat, Kryten walks behind him. Kryten would have had to walk past Rimmer in the previous shot to get there yet we did not see him while Rimmer was talking. (00:13:15)
Revealing mistake: During the scene in the space station's dining room, when Craig Charles is making a speech explaining that they should escape, he stands up and pours himself a glass of Bucks Fizz. Craig fills the glass too soon (half way through the speach) and must realise, as he pours the drink back into the pitcher, and then begins filling his glass again. (00:20:20)
Continuity mistake: When Lister finishes pouring a glass of Bucks Fizz, he begins to place the jug back on the table with his hand still on it, but in the next shot, the jug is now on the table with Lister's hand nowhere near it. (00:20:20)
Visible crew/equipment: When the Red Dwarf crew are talking about who Legion is (after Lister has poured his bucksfizz), Kryten then says, "Could our very presence here have inadvertently awoken him?" As he says this, at the left side of the screen The End of a camera lens pulls away. (00:20:30)
Revealing mistake: When Lister hits Legion over the head, his mask falls off. In the shot that shows Rimmer, Cat and Kryten in the foreground sitting at the table and Lister and Legion in the background, Legion's face can be seen and it is apparent that it is not the combination of the four that is his face, but in fact the actor's real face. (00:21:15)
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