Visible crew/equipment: When talkie Toaster says, 'I toast, therefore I am.', you can see the legs of a crew member moving in the reflection of the toaster. (00:04:40 - 00:11:50)
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