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)
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)
Continuity mistake: When Legion puts his mask back on, just as he says "Kryten knows", the mask is not properly fixed on, leaving his chin exposed, but when the camera is on him next, the mask is suddenly fixed into place. (00:21:35)
Gunmen of the Apocalypse - S6-E3
Continuity mistake: Just after the virus infects the ship, the Cat is looking straight forwards. In the next shot he is looking to the far left at Lister. (00:10:45)
Gunmen of the Apocalypse - S6-E3
Continuity mistake: When Lister says the escape pod is not an option, his hands are apart in front of him. In the next shot, they are together. (00:12:20)
Gunmen of the Apocalypse - S6-E3
Continuity mistake: When Lister tells Rimmer that the escape pod is not an option, Lister is looking at Rimmer, but in the next shot, he is looking down at Kryten. (00:12:20)
Gunmen of the Apocalypse - S6-E3
Continuity mistake: When the Apocalypse boys shoot the bottle out of Kryten's hand, you can see Kryten drop the bottle neck. In the next shot he is still holding it. (00:14:45)
Gunmen of the Apocalypse - S6-E3
Continuity mistake: When Lister enters the bar, he goes through the swing doors and they close behind him. In the interior shot Both Lister and the Cat have gone though the swing doors. (00:17:10)
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