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)
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)
Continuity mistake: As Ace Rimmer is leaving, the Cat priest has his arms behind his back. In the next shot they are in front of him. (00:06:10)
Continuity mistake: When Ace Rimmer is talking to the Cat as a priest, the Cat has the pipe in his mouth in one shot, then he is holding it in front of him in the next. (00:03:45)
Visible crew/equipment: When Rimmer is speaking to Lister about how Ace Rimmer got all the breaks in his life, a boom mic can be seen in the top left of the screen. (00:24:15)
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