Rimmerworld - S6-E5
Continuity mistake: At The End of the episode, when Lister says, 'I'm saying nothing man, don't want to spoil the surprise,' his hood and locks are arranged completely different than all other shots in the scene. (00:27:20)
Visible crew/equipment: When the crew leave the Red Dwarf game area, a boom mic is visible in the top right hand corner. (00:11:35)
Revealing mistake: During the last scene of the episode, the Cat keeps brushing against Rimmer's hologramatic shirt. (00:27:10)
Continuity mistake: When the Cat leaves Lister's quarters after showing him the cat book, one of Lister's locks is hanging over his right shoulder. In the next shot it is gone. (00:11:40)
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)
Out Of Time - S6-E6
Visible crew/equipment: When Kryten walks into the cockpit to offer Lister a beer, a boom mic can be seen at the top of the screen by Kryten's head. (00:10:05)
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)
Revealing mistake: When Lister uploads his memories, the wide shot shows various videos of Rimmer in the background, but in the close up it shows a plain white screen. (00:17:55)
Continuity mistake: When the Nazi commander throws the crocodile at Ace, the yellow curtain is behind ace as he falls. In the next shot, the yellow curtain is in front of him. It is clear he did not fall through the curtain as it does not move as he hits the floor. (00:01:00)
Emohawk - Polymorph II - S6-E4
Visible crew/equipment: After the crash when Lister comes in from outside, as he says 'it's waist high out there', a boom mic can be seen at the top of the screen. (00:09:30)
Out Of Time - S6-E6
Visible crew/equipment: At the start of the episode when Rimmer says 'any objections?' a boom mic can be seen moving across the top of the screen. (00:01:25)
Visible crew/equipment: When the Cat shoots the locker which the low Lister is hiding at The End of the episode, a boom mic can be seen above the Cat. (00:25:40)
Confidence and Paranoia - S1-E5
Continuity mistake: When the Cat visits Lister, Lister puts his arm down on the bed, but in the next shot he is leaning on his hand. (00:14:45)
Revealing mistake: When the simulant hits Able over the head with the steel bar, you can clearly see it bend. He hits him a second time a few moments later and it is straight again. (00:14:45)
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