Continuity mistake: When the group are about to open the door with the heat seeking missiles inside and the Polymorph sneaks up behind them, Lister is standing at the front of the group, Cat and Kryten are behind Lister and Rimmer is standing at the back, behind all three. In the next shot, as the missiles exit the door, Rimmer is now suddenly standing front of Cat. (00:24:40)
Revealing mistake: When Rimmer is piloting Starbug in Lister's body, there is a shot of Starbug spinning in circles. This is a shot that was taken from S3 E2 Marooned, of Starbug crashing after colliding with the asteroid. The only difference is the planet in the background has been changed. (00:22:10)
Continuity mistake: When Lister (in Rimmer's body), Cat and Kryten are chasing Rimmer in Blue Midget, the exterior shot shows all three sitting in one row. From the interior, Cat is sitting in front of Lister and Kryten, and Lister and Kryten are sitting behind Cat. (00:22:40)
Continuity mistake: When Rimmer (in Lister's body), is driving Starbug through the moon, the others are following in Blue Midget. One shot shows Blue Midget directly behind Starbug, but another shot shows Blue Midget much further to the right. (00:23:10)
Timeslides - S3-E5
Continuity mistake: When Kryten notices the photo of the bike in the countryside is moving, the peg attached to it is near the middle, along the top, but in the shot from behind, the peg is much closer to the right. The same goes for the photo of Kryten's birthday party. (00:03:30)
Revealing mistake: During the chase on the moon, there is a shot from in front of Starbug crashing into an asteroid. About twenty seconds after this, the exact same shot of Starbug crashing into an asteroid is been repeated a second time, when the ship crashes. (00:23:20)
Timeslides - S3-E5
Continuity mistake: When Lister and Gilbert are looking at the statue of Lister in the courtyard, Lister has his arms crossed in an angle from above, but when the shot cuts back, his arms are at his side, before crossing them again. (00:19:25)
The Last Day - S3-E6
Audio problem: When Lister tries to shoot Hudzen, Hudzen grabs Lister and throws him, but a punch sound effect can be heard, despite no punch being made. (00:26:15)
Timeslides - S3-E5
Continuity mistake: When Lister is looking through Hitler's briefcase, he finds a banana and crisps sandwich with a bite taken from it. When Rimmer takes a bite out of the same sandwich later in the episode, the sandwich is whole. (00:08:30 - 00:26:15)
Continuity mistake: When the Polymorph is switching between various appearances at the start, it stops at a rabbit. When the Polymorph stops at the rabbit, there is a damp stain beside the two yellow lines on the floor. This damp stain was not there when the Polymorph was switching between other forms. The stain just suddenly appears out of nowhere. (00:01:45)
Audio problem: When Kryten starts looking over Lister's bunk trying to find the Polymorph, posing as the boxers, the boxers, and therefore the Polymorph, are visible on the bunk. The sound of the Polymorph transforming is heard, indicating the Polymorph has changed form, but the boxers remain there, without any transformation. It is not until a few shots after that the Polymorph has appeared to have changed form. (00:10:00)
Continuity mistake: After Starbug and Blue Midget leave Red Dwarf, there is a shot of Blue Midget driving away from the ship, towards the camera. Cat and Kryten are the only two on board as Rimmer and Lister are on Starbug, but there are three people shown inside Blue Midget. This is because the shot was taken from series two, in which Rimmer, Lister and Cat were inside it. (00:03:25)
Continuity mistake: When Lister is telling Rimmer that he is going to die and that Rimmer doesn't need food, there is snow over his face, hair and coat collar, but a few seconds later, the snow has mostly disappeared. (00:09:35)
Continuity mistake: When Rimmer stresses out while preparing for his exam, he puts his hands on his face, and screams whilst starting to bend over. In the next shot, Lister wakes up, and Rimmer is suddenly standing upright. (00:13:20)
Continuity mistake: When Holly interrupts Rimmer learning Esperanto saying "The menu looks interesting", he appears on the TV screen, with his chin blocked by the edge of the frame. The shot then cuts to a view of the screen, and his entire face is suddenly fully in the frame. (00:05:00)
Stasis Leak - S2-E4
Continuity mistake: In the lift, when the woman in the video is explaining how the lift works, she mentions "a bag will drop containing sedatives and cyanide capsules", pointing upwards. The shot cuts to Lister, and the woman in the video can be seen to the left of shot, with her arms at her side. (00:08:35)
Stasis Leak - S2-E4
Continuity mistake: When Lister is in the hotel room with future Lister and Kochanski, Lister says he came because he thought he was going to get married whilst talking to future Lister, but in the next shot, Lister's facial expression has suddenly changed and is now looking more confused. (00:25:35)
Stasis Leak - S2-E4
Continuity mistake: When future Lister is making Lister and Cat leave the hotel room, Lister begins talking to future Lister about living his life. Future Lister is standing beside the door in one shot, but has his head suddenly resting on the door in the next shot. (00:26:25)
Other mistake: The shots of Blue Midget driving back to Red Dwarf that are shown from behind are visibly the exact same shots used each time. This is evident as the driving movements of Blue Midget, its position in the frame, and Red Dwarf's position in the background are all identical each time.
Visible crew/equipment: When Lister steps back inside the observation room after Rimmer leaves, a stage light can be seen reflected in the window-like light fixture on the wall. It can't be a light on the ship as none of the lighting on Red Dwarf is in the shape of the light seen in the reflection. (00:14:05)
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