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)
Revealing mistake: When Holly gives Rimmer a new uniform, during the switch, Holly can be seen to jolt on his screen in the background. (00:03:20)
Other mistake: When the Cat says there better be no dogs on the ship, there are only about two or three stars visible out the window. Far too few given the amount of stars shown in exterior space shots of the ship. (00:05:15)
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: The cuts on Lister's robot goldfish disappear when he throws it back into the tank after fixing it. (00:06:00)
Revealing mistake: When Holly gives Rimmer a new haircut, Rimmer salutes and touches his hair with his hand. Surely he would have noticed his hair has become much longer, especially after he asked for a crew cut. (00:07:00)
Continuity mistake: Both Rimmer and Lister go through a door on the right hand side of the captain's office which wasn't there in the previous episode. (00:10:20)
Visible crew/equipment: Just after Lister hits the toaster, a pair of legs can be seen moving in it's reflection a moment before the scene ends. (00:11:30)
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)
Continuity mistake: Just before Lister cuts himself shaving, he is shaving away from himself. The camera changes and he is shaving in the oposite direction. (00:13:00)
Continuity mistake: The sign above the stasis booth in this episode is different than what it was in the previous episode, "The End". (00:14:00)
Continuity mistake: When Lister sees the future echo in the drive room, Rimmer points when he says 'Shut up.' However when the scene plays out again, Rimmer's arms stay down by his sides. (00:15:00 - 00:16:00)
Visible crew/equipment: When both Rimmer and his future echo walk through the door from the captain's office, the edge of the set can be seen. (00:15:09 - 00:16:04)
Audio problem: In Rimmer's future echo he says, "You're space crazy", but in the real conversation with Lister, he actually says, "You are space crazy". (00:15:20 - 00:16:15)
Continuity mistake: When the Cat's future echo says, "I think I lost my tooth," he is at The End of the corridoor. When the present Cat say it, he is just leaving the sleeping quarters. (00:16:30 - 00:22:25)
Visible crew/equipment: When talkie toaster says 'light speed' a crew member can be seen in its reflection wearing a yellow t-shirt and jeans. (00:17:35)
Revealing mistake: In the drive room when Lister kicks the vending machine after he finds out he's going to die, you can see the shadow of the machine wobbling as if it were lightweight. (00:20:20)
Visible crew/equipment: Just before Rimmer sends his 'Internal Memo' Lister is standing next to his fish tank in the sleeping quarters. In the relection of the glass you can see pages being looked through by a member of the crew. (00:23:15)
Other mistake: When Rimmer is doing Lister's memo, there there are only about a few stars visible out the window, which is far too few given the amount of stars shown in exterior space shots of the ship. Additionally, a star suddenly appears in the window. (00:23:15)
Continuity mistake: At The End of the episode, when the future Lister and the babies appear, Rimmer has his arms folded. In the next shot, Rimmer's hands are on his hips. Also, Lister's locks change positions. (00:27:50)
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