Revealing mistake: When the ship crashes into the snow planet, a wire can be seen attached to it as it crashes.
Revealing mistake: When Kryten's head explodes, you can tell the head is a dummy. (00:08:05)
Revealing mistake: When the simulant hits Able over the head with the steel bar, you can clearly see it bend. He hits him a second time a few moments later and it is straight again. (00:14:45)
Revealing mistake: When Able screws on Kryten's head he only turns it once, yet in Tikka To Ride, Lister screws his head on at least twice around. (00:15:30)
Revealing mistake: When Lister kicks the simulant in the head, you can see he misses him by about a foot. (00:20:00)
Revealing mistake: When Kryten's hand inflates and flies away, his forearm bends in the middle. (00:06:40)
Revealing mistake: When Rimmer puts the engaged blindfold on and sits on the toilet, he doesn't take his trousers down. (00:03:50)
Revealing mistake: The first time you see Lister, the Cat, Kochanski and Kryten in the AR machine you can see the cat opening his eyes realising that it is not in the script, smiling and then closing his eyes. (00:04:50)
Revealing mistake: Just before the Cat starts his dance, Kochanski is at the back of the cockpit of Blue Midget and is bouncing up and down, yet the ship is not moving. When it starts moving, Kochanski is sitting still. (00:08:05)
Revealing mistake: After the Cat's dance, Lister says 'we are outta here' and pulls the level, at which point the crew all fall back as if Blue Midget had rushed forwards. However, in the model shot of the ship it shows it scraping its foot on the floor before it runs forwards, meaning the crew should not have fallen back in their seats. (00:10:50)
Revealing mistake: When Rimmer is typing on the keyboard, what he is saying does not match what he is typing. He is typing randomly. (00:12:20)
Revealing mistake: In the scene where Kochanski, the Cat, and Kryten first discover the time wand, there are a group of Canaries who are frozen in time from its effects. In the first shot of these people, the woman on the far right of the screen blinks her eyes. (Confirmed on DVD commentary). (00:15:50)
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