Continuity mistake: When Rimmer and Lister leave their sleeping quarters, there are two pictures on the wall between the door and the window and a canister on the wall beside the beds. When they are next in the room the items are gone, and at The End of the episode they have all returned. (00:09:20 - 00:12:50)
Continuity mistake: When the Cat is eating the food set out by Lister, there is a cloth on the table. When Lister is asking where the other kitties are, the cloth is shown near the centre of the table. Rimmer then says he wants it off the ship, and the cloth is suddenly further to the right of the table. (00:27:45)
Continuity mistake: When Lister goes into stasis, Todd Hunter turns the wheel on the door to lock Lister in. In the next scene when Lister awakes from stasis, he just pushes the door open without turning the wheel to unlock it. Even if we are to assume that Holly would automatically open the door, the wheel should still turn to unlock the mechanism.
Continuity mistake: When Rimmer stresses out while preparing for his exam, he puts his hands on his face, and screams whilst starting to bend over. In the next shot, Lister wakes up, and Rimmer is suddenly standing upright. (00:13:20)
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