Reketrebn was one of the Symbi-morphs who were aboard the Mayflower to terraform a planet in the Andromeda galaxy. She and the other man-made life forms aboard staged a mutiny which overthrew the Human crew and forced the ship into a parallel universe. The GELFs then abandoned the Mayflower and populated a nearby asteroid belt, which would come be known as the Great GELF State.
When Dave Lister was imprisoned on the Cyberia penal colony, the authorities offered him a pardon if he would help terraform and settle a planet to allow the GELFs to pass through the Omnizone. As part of his reward, he was allowed to spend 24 hours with a Symbi-morph, a shape-shifting telepath that would fulfill his every desire. Unfortunately, the only one available was Reketrebn.
Reketrebn was an unbroken Symbi-morph who refused to obey her host, a Dingotang named Deki . He had four of Reketrebn's five hooks, psychic connectors which allowed her to read the thoughts of others. She refused to serve Lister or anyone but Deki, which infuriated Deki and made him abusive towards her. He insisted she serve anyone he wanted and beat her if she did not. In order to avoid entering Lister's cell, she turned into a sofa. After Deki forced her inside, she sullenly became a pile of yak dung out of spite, but used her last hook on Lister.
Lister wasn't interested in Reketrebn's pleasurising abilities, not even when she became Kochanski. He was more interested in getting her help in escaping. By becoming Kryten, she could advise Lister on how to escape, drawing on Lister's own subconscious deductions and observations and voicing them as Kryten to make him feel more confident in his current plan. Asking her to morph into Lister, she could feel his pain and agreed to help him.
Lister and Reketrebn used her powers to escape the cells onto a transport ship. Unfortunately, it was the very ship that they were trying to avoid, headed for the GELF planet. When they arrived, Lister and Reketrebn escaped the Rage and were captured by Michael McGruder and his group. She helped them overcome the Rage and started to head for the caves to ride out the passage through the Omnizone. Reketrebn then joined them and the Red Dwarf crew in taming the new planet.
Reketrebn was devoted to her primary host, Deki. She wished only to serve him, being sullen and petulant towards Lister when Deki insisted she please another. She later became resigned to serving Lister, morphing into people and things to make him feel better. After she mimicked his form, she felt his pain and agreed to help him, becoming his trusty companion.
Reketrebn had the ability to morph into almost anyone or anything. She could do this at will or at the request of someone with one of her psychic hooks implanted above their eyebrow. She could become specific people, but only with the knowledge of her host (she could mimic Kryten, but didn't know all the things that Kryten knew as she was only drawing on Lister's perception of him). However, she was also able to draw on subconscious observations rather than conscious knowledge, telling Lister everything he knew about symbi-morphs based on information he had picked up from a bar conversation even if he wasn't consciously aware of hearing it.
She could mimic glass, fire, electronic keycards, horses, lifts, liquids, dung, flowers, furniture and almost any person, but her neutral form was that of a lightly matrixed black and white humanoid.