Rimmerworld - S6-E5
Continuity mistake: When Kryten, the Cat and Lister teleport when the ship is disintergrating, Lister's locks are over his right shoulder. When they arrive, his locks are behind his back. (00:12:40)
Rimmerworld - S6-E5
Visible crew/equipment: When Starbug goes through the wormhole, a boom mic shadow can be seen on the back wall next to Kryten. (00:20:20)
Continuity mistake: When Lister is choking the Cat, he says 'give me a break, Rimmer'; at this point Rimmer is looking at the Cat and Lister, yet in the next shot he is looking at Kryten. (00:22:50)
Continuity mistake: The bottle of chloroform Kryten uses to take Lister by surprise appears from nowhere. (00:23:30)
Revealing mistake: When Rimmer and Lister are in the observation dome, background stars can be seen on Lister's locks and on the top of his forehead. (00:25:40)
Continuity mistake: When Ace drives the bike out of the shed, the piece of wood is between the front wheel and the handlebars. In the next shot, the piece of wood is resting on his arms. (00:03:25)
Continuity mistake: When Rimmer's mother is talking to him while he is hung upside down, she is stood about a foot away from him in one shot, then in the next she is about three feet away. (00:01:45)
Stasis Leak - S2-E4
Revealing mistake: At The End of the episode when the future Lister closes the door on the Cat and Lister, you can see the partial editing out of Lister and the Cat as the door closes. As this happens, Lister and the Cat disappear before the door has passed them. (00:26:50)
Continuity mistake: When Lister and the Cat first see Lisa Yates on the screen, their shoulders are together. In the next shot there is a wide gap between them. (00:18:30)
Revealing mistake: When the Cat, Lister and Kryten are walking and the Cat is complaining about rock, keep an eye on the background. They start walking just before a set of steps, then do a complete loop back to the steps for no reason. (00:06:15)
Revealing mistake: When Kryten's head explodes, you can tell the head is a dummy. (00:08:05)
Emohawk - Polymorph II - S6-E4
Continuity mistake: The Cat's earrings disappear when the emohawk attacks him. (00:20:00)
Revealing mistake: When Ghandi explodes, there is a single shot where he had disappeared before the explosion goes off. (00:22:35)
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