Continuity mistake: When Lister keeps using the time wand on Captain Hollister several times, he keeps saying "See you in 10 minutes" several times. Every time Hollister says the line, the way he delivers the line keeps changing. (00:12:55)
Continuity mistake: When Kill Crazy and Baxter are about to beat up Rimmer and Lister, as Baxter says "Say goodbye to your teeth", Kill Crazy has his hand pressed against Rimmer's jaw, advancing his face towards Rimmer's, but when Baxter goes to punch Lister, Kill Crazy's hand is by his side and is stood away from Rimmer. (00:19:50)
Continuity mistake: When Baxter tries to punch Lister the first time and fails, Kill Crazy is looking at Lister with his arms by his side, but in the next shot, Kill Crazy is now looking at Rimmer and doing motioning actions with his arms and face. (00:19:55)
Continuity mistake: When Hollister picks up the lemon drink, his left hand is by his side. In the next shot it is on his chest. (00:01:50)
Continuity mistake: When Rimmer gives Hollister the directives to sign, he holds the clipboard in both hands. In the next shot his left hand is under the first page. (00:02:15)
Continuity mistake: Just before Rimmer and Lister drink the hooch, Lister's locks are behind his back, then one of the locks moves to in front of his left shoulder during a brief shot of Rimmer. (00:13:30)
Continuity mistake: When Howard and Crawford are transported to Trojan, two of the three teleporter doors are open. When Crawford goes through the teleporter, one of the three doors close. Yet when Cat puts the resentment file into Crawford's neck, she starts shooting at everything including the teleporters, and now all the doors are open. (00:23:00 - 00:26:30)
Continuity mistake: When Lister notices the video, the silhouette of a flashing blue light is cast on the table (to the left of screen). In the next shot, there is no sign of the flashing blue light. (00:10:40)
Continuity mistake: When the book "Roots of Coincidence" is first seen it's a paperback but later in the episode it's suddenly a hardback.
Continuity mistake: Rodon is revealed to be the Cat's older brother, and the rebelling cats refer to the Red Dwarf itself as the ship of their birth, but in Psirens, it was revealed that the crew spent 200 years in deep sleep while tracking Red Dwarf. This appears to have been forgotten.
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