White Hole - S4-E4
Continuity mistake: When Holly is talking to the toaster and they say about currenty bread, the toaster's handle is half way down. In the next shot it is at the top. (00:08:00)
Continuity mistake: When the wax droids charge at the start of the battle, Santa, Marilyn Monroe and Pope Gregory charge forward, but in the next shot, Marilyn Monroe is running on her own. (00:22:35)
Continuity mistake: When Camille asks Kryten if they could make it, Kryten puts his glass down on the table. In the next shot, it is suddenly back in his hand, being put back down again. (00:22:35)
Continuity mistake: Lister enters with a tray with some food on to give to Kryten. The position of the tray changes position between shots. (00:10:10)
Continuity mistake: When Lister has been made smaller, one shot shows him holding the bazooka, but the next shot shows him with his hand lowered. (00:25:30)
Continuity mistake: When Lister sarcastically thanks the Cat for visiting him, Lister looks forwards, but in the next shot is looking at the Cat. (00:03:35)
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