Visible crew/equipment: When Rimmer is getting in the car on the beach, you can see the cameraman's reflection on the side of it. (00:18:25)
Continuity mistake: When Lister is fixing his robot goldfish, he picks it up with his right hand, then after the camera cuts, he puts it back into the tank with his left hand. (00:06:00)
Continuity mistake: When the crew almost kill themselves, Kryten is holding the harpoon gun to his head. The point of the spear is missing but in the next shot it has reappeared. (00:23:30)
Revealing mistake: When the Dalai Lama explodes, there is a single shot where he has disappeared and a yellow cloth has taken his place just before the explosion. The cloth then lands in the background. (00:22:55)
Timeslides - S3-E5
Revealing mistake: When Lister is hit in the face with the snowball, some of the snow lands on Rimmer's hologramatic uniform. (00:07:40)
Stasis Leak - S2-E4
Revealing mistake: Rimmer, Lister and the Cat are not visible in the mirror when the crew member finds them in the shower. (00:10:25)
Continuity mistake: Just after Kryten says 'you bet your ass' he is holding onto his groinal attachment over his shoulder. In the next shot, his arm is lowered. (00:12:00)
Continuity mistake: When Lister rides his bike in the first scene, there is a Union Jack just behind his seat. When he stops, a US flag has appeared below it. (00:01:45)
Continuity mistake: The cuts on Lister's robot goldfish disappear when he throws it back into the tank after fixing it. (00:06:00)
Continuity mistake: When Lister cuts himself shaving he moves his locks behind his back, then in the next shot, they are over his shoulder again. (00:12:55)
Rimmerworld - S6-E5
Visible crew/equipment: When Lister, the Cat and Kryten arrive on Rimmerworld, as the Rimmer guard steps out and says 'silence mutant' a boom mic is visible at the top of the screen. (00:21:05)
Continuity mistake: When Pete eats Bird-man, Bob is with the crew in the cargo bay. When they run away, Bob disappears. (00:27:00)
Continuity mistake: The bottle of chloroform Kryten uses to take Lister by surprise appears from nowhere. (00:23:30)
Visible crew/equipment: When Ace Rimmer is talking to Mellie, a boom mic can be seen at the top of the screen. (00:04:05)
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