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: 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)
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)
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 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)
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: 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: The cuts on Lister's robot goldfish disappear when he throws it back into the tank after fixing it. (00:06:00)
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