Continuity mistake: When Lister swings the axe at The Cat and hits the door frame, the axe head bends. When Lister pulls the axe out, its head is fine again. (00:22:30)
Continuity mistake: When the second version of Allman appears, he has his arms folded. In the next shot, they're down by his side. (00:01:25)
Timeslides - S3-E5
Continuity mistake: We are told that it is impossible to move outside the frame of a slide, yet when we are shown the slide of young Lister and his band, all we see is the band on stage but the crew move freely about the pub. (00:11:40)
Terrorform - S5-E3
Continuity mistake: When Lister, the Cat and Kryten figure out how to escape, Kryten says 'precisely' and raises his right hand. In the next shot, both of his hands are raised. (00:22:15)
Continuity mistake: Able's head bounces off the simulant and lands behind him, yet when Lister sends the gelf and simulant back to their ship, the head is next to him on the floor. (00:20:10)
Terrorform - S5-E3
Continuity mistake: At the start of the episode Kryten has crashed Starbug 1 onto the psi-moon. Lister and the Cat rescue him in Starbug 2, yet when the crew search for Rimmer in the swamp, they are in Starbug 1. (00:06:10 - 00:19:45)
Timeslides - S3-E5
Continuity mistake: When the slideshow starts, the photos in Lister's hands disappear between camera cuts. (00:06:20)
Confidence and Paranoia - S1-E5
Continuity mistake: At the start of the episode, when Lister is watching the film, keep an eye on his milkshake. One moment the glass is on the table, then when the camera cuts, he's drinking from it. (00:02:25)
Terrorform - S5-E3
Continuity mistake: The cutting torch Kryten uses to cut his hand off appears from nowhere. (00:02:20)
The Last Day - S3-E6
Continuity mistake: When Kryten is packing his heads away at the point where he says 'how would the manufacturers sell their latest model?' he is looking forwards. The camera changes angles and he is looking down. (00:04:00)
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: When the ducts are being backwashed, Lister's dreadlocks are on his right shoulder. But when the shot changes and he says "I hate this. I really hate this.", his locks are on his left shoulder. Then the shot changes again and they're back on his right shoulder. (00:23:53)
Continuity mistake: During the Cat's dance, he taps his feet and tilts his head back, which Blue Midget copies. In the next shot Blue Midget is looking downwards and then proceeds to do the same dance it just did in the previous shot. (00:10:00)
Continuity mistake: When the simulant drinks his drink, he lifts the cup up to drink, yet in the next shot he lifts the cup up again, repeating the same action twice between shots. (00:13:50)
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